Ultrasound probe and ultrasound image diagnostic apparatus

ABSTRACT

An ultrasound probe includes: an ultrasound input/output unit to output a transmission ultrasound to a test object by a pulse signal; and a signal input/output unit to output a reception signal when the ultrasound input/output unit receives a reflected ultrasound from the test object, wherein the ultrasound probe is set so that a difference between maximum and minimum values of a group delay in a transmission/reception frequency band at −20 dB of the ultrasonic probe is equal to or less than 0.15 radian, the group delay being obtained from a phase difference for each frequency between the input pulse signal and the reception signal obtained from the reflected ultrasound of the transmission ultrasound output by the pulse signal, or so that a standard deviation of the group delay in the transmission/reception frequency band at −20 dB of the ultrasonic probe is equal to or less than 0.025.

CROSS REFERENCE TO RELATED APPLICATION

This Application claims the priority of Japanese Patent Application No.2014-082675 filed on Apr. 14, 2014, which is incorporated by referenceherein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an ultrasound probe and an ultrasoundimage diagnostic apparatus.

Description of Related Art

According to ultrasound diagnostics, a realtime display of heartbeatand/or motion of a fetus can be executed by a simple operation ofapplying an ultrasound probe to a body surface. Additionally, theultrasound diagnostics are excellent in safety, and enable repeatedexaminations.

With regard to such technique to display ultrasound images, it has beenknown that a high contrast image can be obtained by imaging higherharmonic components (e.g. frequencies 2f₀, 3f₀, etc.) with respect to afundamental component (frequency f₀) of a transmission signal. Thisimaging method is referred to as Tissue Harmonic Imaging.

The higher harmonic components appear mainly due to nonlineardistortions occurring when ultrasound propagates through a test object.Concretely, when the ultrasound irradiates a living body, the ultrasoundsignal is distorted due to a nonlinear response of tissue whilepropagating through the tissue, and thereby the higher harmoniccomponents increase. As a result, a reception signal includes thefrequency 2f₀ which is twice the frequency f₀, and/or the frequency 3f₀which is three times the frequency f₀.

As a method for extracting the higher harmonic components in the TissueHarmonic Imaging, there has been known a filter method and a pulseinversion method.

The filter method extracts, for example, the higher harmonic component2f₀ from the reception signal, by using a bandpass filter having acenter frequency of 2f₀.

The pulse inversion method transmits the first transmission pulse signaland the second transmission pulse signal obtained by polarity inversionor time reversal with a predetermined time interval, and combines thereception signals so that the fundamental components are canceled andthereby the secondary higher harmonic components are emphasized.

In the meantime, there is a problem that the higher harmonic componentscontained in the ultrasound signal are easily influenced by attenuationwhen propagating through a test object because higher harmoniccomponents generally have higher frequencies than that of thefundamental component, and accordingly penetration of the reflectedultrasound signal from a deep part is not good. The penetration can beimproved by lowering the frequency f₀ of the fundamental component so asto suppress the influence of the attenuation, but a tradeoffrelationship occurs in this case, namely, the resolution is degraded.

Among the above two method, the filter method cuts a low frequencyregion without distinction of fundamental wave and higher harmonicswave, and thereby the influence of the attenuation remarkably appears.In addition, the filter method makes the extracted frequency bandnarrower, and accordingly the image quality deteriorates more than thatof the pulse inversion method. For this reason, the pulse inversionmethod has become the mainstream in the devices/apparatuses other thanlow-end devices/apparatuses.

In recent years, there has been proposed a method for improving theimage quality of the ultrasound images by using various kinds of higherharmonic components, for example, by using the secondary higher harmoniccomponent and a differential sound component having a lower frequencythan that of the secondary higher harmonic component so as to cope withthe wider bandwidth ultrasound in the above-described pulse inversionmethod (for example, see Japanese Patent Application Laid-OpenPublication No. 2002-301068).

However, the technique described in Japanese Patent ApplicationLaid-Open Publication No. 2002-301068 has the problem that when theplural kinds of higher harmonic components are used, cancellation amongthe plural higher harmonics waves occurs due to group delaycharacteristics of the ultrasound probe. As a result, an intendeddistance resolution cannot be always obtained.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an ultrasound probe andan ultrasound image diagnosis apparatus which can obtain ultrasoundimages having an excellent distance resolution by reducing cancellationamong a plurality of kinds of higher harmonics waves.

To achieve at least one of the above objects, an ultrasound probereflecting a first aspect of the present invention includes: anultrasound input/output unit to output a transmission ultrasound to atest object in response to an input of a pulse signal; and a signalinput/output unit to output a reception signal when the ultrasoundinput/output unit receives a reflected ultrasound from the test object,wherein the ultrasound probe is set so that a difference between amaximum value and a minimum value of a group delay in atransmission/reception frequency band at −20 dB of the ultrasonic probeis equal to or less than 0.15 radian, the group delay being obtainedfrom a phase difference for each frequency between the input pulsesignal and the reception signal obtained from the reflected ultrasoundof the transmission ultrasound output by the pulse signal, or so that astandard deviation of the group delay in the transmission/receptionfrequency band at −20 dB of the ultrasonic probe is equal to or lessthan 0.025.

Preferably, in the ultrasound probe, a fractional bandwidth at −20 dB is120% or more.

An ultrasound image diagnosis apparatus reflecting a second aspect ofthe present invention includes: an ultrasound probe which outputs atleast one transmission ultrasound to a test object in response to aninput of at least one pulse signal, and outputs at least one receptionsignal when at least one reflected ultrasound from the test object isreceived; and a transmission section which outputs a pulse signal of apredetermined driving waveform so as to cause the ultrasound probe togenerate the transmission ultrasound, wherein the transmission sectionoutputs the pulse signal of the driving waveform according to which adifference between a maximum value and a minimum value of a group delayobtained from a phase difference in each frequency, in a frequency bandwhere a frequency band included in a transmission/reception frequencyband at −20 dB of the ultrasound probe and a frequency band at −20 dB ofthe driving waveform in the pulse signal overlap each other, is equal toor less than 0.15 radian, or according to which a standard deviation ofthe group delay in the frequency band where the frequency band includedin the transmission/reception frequency band at −20 dB of the ultrasoundprobe and the frequency band at −20 dB of the driving waveform in thepulse signal overlap each other is equal to or less than 0.025.

An ultrasound image diagnosis apparatus reflecting a third aspect of thepresent invention includes: an ultrasound probe which outputs atransmission ultrasound to a test object in response to an input of apulse signal, and outputs a reception signal when a reflected ultrasoundfrom the test object is received; and a transmission section whichoutputs a pulse signal of a predetermined driving waveform so as tocause the ultrasound probe to generate the transmission ultrasound,wherein the ultrasound probe and the driving waveform of the pulsesignal output from the transmission section are set so that a differencebetween a maximum value and a minimum value of a totaling value in afrequency band where a frequency band included in atransmission/reception frequency band at −20 dB of the ultrasound probeand a frequency band at −20 dB of the driving waveform in the pulsesignal overlap each other is equal to or less than 0.15 radian, thetotalizing value being obtained by totalizing a group delay obtainedfrom a phase difference in each frequency between the pulse signal inputto the ultrasound probe and the reception signal obtained from thereflected ultrasound of the transmission ultrasound output by the pulsesignal and a group delay obtained from a phase difference in eachfrequency of the pulse signal output by the transmission section.

Preferably, in the ultrasound image diagnosis apparatus, the ultrasoundprobe is set so that a difference between a maximum value and a minimumvalue of a group delay in the transmission/reception frequency band at−20 dB of the ultrasound probe is equal to or less than 0.15 radian, thegroup delay being obtained from a phase difference in each frequencybetween the input pulse signal and the reception signal obtained fromthe reflected ultrasound of the transmission ultrasound output by thepulse signal, or so that a standard deviation of the group delay in thetransmission/reception frequency band at −20 dB of the ultrasound probeis equal to or less than 0.025, and the transmission section outputs thepulse signal of the driving waveform according to which a differencebetween a maximum value and a minimum value of a group delay obtainedfrom a phase difference in each frequency, in a frequency band where afrequency band included in a transmission/reception frequency band at−20 dB of the ultrasound probe and a frequency band at −20 dB of thedriving waveform in the pulse signal overlap each other, is equal to orless than 0.15 radian, or a standard deviation of the group delay in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeand the frequency band at −20 dB of the driving waveform in the pulsesignal overlap each other is equal to or less than 0.025.

Preferably, in the ultrasound image diagnosis apparatus, thetransmission section outputs the pulse signal of the driving waveform inwhich the frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeand the frequency band at −20 dB of the driving waveform in the pulsesignal overlap each other covers 70% or more of a transmission/receptionfrequency bandwidth at −20 dB of the ultrasound probe.

Preferably, in the ultrasound image diagnosis apparatus, thetransmission section outputs the pulse signal of the driving waveformwhose period is equal to or more than 1.5.

Preferably, in the ultrasound image diagnosis apparatus, thetransmission section outputs the pulse signal of the driving waveformwhose pulse duration is equal to or more than a time corresponding totwo periods at a center frequency of the transmission/receptionfrequency band at −20 dB of the ultrasound probe.

Preferably, in the ultrasound image diagnosis apparatus, thetransmission section outputs the pulse signal according to a controlsignal of five values or less.

Preferably, in the ultrasound image diagnosis apparatus, thetransmission section outputs the pulse signals of different drivingwaveforms to a same scanning line with a predetermined time interval forplural times, and the ultrasound image diagnosis further includes animage generating section to combine the reception signals obtained fromthe reflected ultrasounds of the transmission ultrasounds generated bythe plural pulse signals to generate an ultrasound image data based onthe combined reception signals.

Preferably, in the ultrasound image diagnosis apparatus, thetransmission section outputs the pulse signals whose driving waveformshave an asymmetric relationship with each other to the same scanningline with the predetermined time interval for plural times.

Preferably, in the ultrasound image diagnosis apparatus, thetransmission section outputs the pulse signal including intensity peaksof a frequency power spectrum on a low frequency side and on a highfrequency side with respect to a center frequency of thetransmission/reception frequency band at −20 dB of the ultrasonic probe.

Preferably, in the ultrasound image diagnosis apparatus, thetransmission section outputs the pulse signal including two or more ofintensity peaks of a frequency power spectrum on the high frequency sidewith respect to the center frequency of the transmission/receptionfrequency band at −20 dB of the ultrasound probe.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the appended drawings, andthus are not intended as a definition of the limits of the presentinvention, and wherein:

FIG. 1 is a diagram illustrating an external configuration of anultrasound image diagnosis apparatus;

FIG. 2 is a block diagram illustrating a schematic configuration of theultrasound image diagnosis apparatus;

FIGS. 3A and 3B are diagrams each explaining transmission/reception bandcharacteristics and group delay characteristics of an ultrasound probe;

FIG. 4 is a block diagram illustrating a schematic configuration of atransmission section;

FIG. 5 is a diagram explaining a driving waveform of a pulse signal;

FIGS. 6A, 6B, 6C and 6D are diagrams each explaining a relationshipbetween a transmission/reception band of the ultrasound probe and thedriving waveform of the pulse signal;

FIGS. 7A, 7B and 7C are diagrams each explaining driving waveformcharacteristics;

FIG. 8 is a graph illustrating a relationship between a frequency and atime corresponding to two periods of the frequency;

FIGS. 9A, 9B and 9C are diagrams each illustrating characteristics of anultrasound probe A;

FIGS. 10A, 10B and 10C are diagrams each illustrating characteristics ofan ultrasound probe B;

FIGS. 11A, 11B and 11C are diagrams each illustrating characteristics ofan ultrasound probe C;

FIGS. 12A, 12B and 12C are diagrams each illustrating characteristics ofan ultrasound probe D;

FIGS. 13A, 13B and 13C are diagrams each illustrating characteristics ofa driving waveform A;

FIGS. 14A, 14B and 14C are diagrams each illustrating characteristics ofa driving waveform B;

FIGS. 15A, 15B and 15C are diagrams each illustrating characteristics ofa driving waveform C;

FIGS. 16A, 16B and 16C are diagrams each illustrating characteristics ofa driving waveform D;

FIGS. 17A, 17B and 17C are diagrams each illustrating characteristics ofa driving waveform E;

FIGS. 18A, 18B and 18C are diagrams each illustrating characteristics ofa driving waveform F;

FIGS. 19A, 19B and 19C are diagrams each illustrating characteristics ofa driving waveform G;

FIGS. 20A, 20B and 20C are diagrams each illustrating characteristics ofa driving waveform H;

FIG. 21 is a diagram illustrating a totaling result of a group delay ofthe ultrasound probe A and a group delay of the driving waveform A;

FIG. 22 is a diagram illustrating a totaling result of a group delay ofthe ultrasound probe B and a group delay of the driving waveform B;

FIG. 23 is a diagram illustrating a totaling result of a group delay ofthe ultrasound probe A and a group delay of the driving waveform G;

FIG. 24 is a graph illustrating a relationship between a frequency and atime corresponding to two periods of the frequency;

FIGS. 25A and 25B are diagrams each illustrating a relationship betweena difference and an evaluation result, the difference being between themaximum value and the minimum value of the totaling result of the groupdelay of the ultrasound probe and the group delay of the drivingwaveform;

FIGS. 26A and 26B are diagrams each illustrating a relationship betweena standard deviation of the group delay of the ultrasound probe and theevaluation result;

FIGS. 27A and 27B are diagrams each illustrating a relationship betweena difference between the maximum value and the minimum value of thegroup delay of the ultrasound probe and the evaluation result;

FIGS. 28A and 28B are diagrams each illustrating a relationship betweena standard deviation of the group delay of the driving waveform and theevaluation result;

FIGS. 29A and 29B are diagrams each illustrating a relationship betweena standard deviation of the group delay of the driving waveform and theevaluation result;

FIGS. 30A and 30B are diagrams each illustrating a relationship betweena difference between the maximum value and the minimum value of thegroup delay of the driving waveform and the evaluation result; and

FIGS. 31A and 31B are diagrams each illustrating a relationship betweena difference between the maximum value and the minimum value of thegroup delay of the driving waveform and the evaluation result.

PREFERRED EMBODIMENT OF THE PRESENT INVENTION

Hereinafter an ultrasound image diagnosis apparatus according toembodiments of the present invention will be described with reference tothe drawings. In this regard, however, the scope of the invention is notlimited to the illustrated examples. The same functions andconfigurations are described with the same reference characters,respectively, in the following descriptions, and redundant descriptionsare omitted.

An ultrasound image diagnosis apparatus S of this embodiment is equippedwith an ultrasound image diagnosis apparatus body 1 and an ultrasoundprobe 2, as illustrated in FIGS. 1 and 2. The ultrasound probe 2includes an ultrasound input/output unit 21 which transmits anultrasound (transmission ultrasound) to a not-illustrated test objectsuch as a living body, and receives a reflected wave (reflectedultrasound: echo) reflected on the test object. The ultrasound imagediagnosis apparatus body 1 is connected to a signal input/output unit 22of the ultrasound probe 2 via a cable 2. The ultrasound image diagnosisapparatus body 1 transmits an electrical driving signal to the signalinput/output unit 22 of the ultrasound probe 2 so as to cause theultrasound probe 2 to transmit the transmission ultrasound to the testobject, and images an internal state of the test object as an ultrasoundimage based on an electrical reception signal generated by theultrasound probe 2 in response to the reflected ultrasound received bythe ultrasound probe 2 from the inside of the test object.

The ultrasound probe 2 has a composition including, for example, abacking layer, piezoelectric layer, acoustic matching layer and acousticlens, which are laminated. The piezoelectric layer is equipped withoscillators 2A each including a piezoelectric device(s), and theoscillators 2A are arranged, for example, in one-dimensional array statein an orientation direction. This embodiment uses the ultrasound probe 2including 192 oscillators 2A. Alternatively, the oscillators 2A can bearranged in two-dimensional array state. The number of the oscillators2A can be arbitrary set. This embodiment adopts an electronic scan probeof linear scanning type as the ultrasound probe 2. Alternatively, eitheran electronic scanning type or a mechanical scanning type may beadopted, and any of a linear scanning type, sector scanning type andconvex scanning type may be adopted. The effects of this embodiment areincreased by adopting the ultrasound probe which can execute broadbandtransmission of the ultrasound with good sensitivity to obtain a highresolution transmission ultrasound, and thereby the ultrasound imagehaving better qualities can be obtained. The bandwidth of the ultrasoundprobe can be arbitrary set. Preferably, a fractional bandwidth at −20 dBis 120% or more.

This embodiment uses the ultrasound probe having group delaycharacteristics according to which a difference between the maximumvalue and the minimum value of the transmission/reception frequency bandat −20 dB is 0.15 radian or less.

The group delay characteristics of the ultrasound probe means groupdelay characteristics in a transmission/reception result of theultrasound, and can be obtained from a phase difference, for eachfrequency, between an electrical signal applied to the ultrasound probeand an electrical signal obtained as a result of transmission/receptionof the ultrasound.

Specifically, for example, in the ultrasound probe having thetransmission/reception band characteristics illustrated in FIG. 3A, thelower limit frequency (FL20) at −20 dB is 3.99 MHz, and the upper limitfrequency (FH20) at −20 dB is 19.72 MHz. Thus, thetransmission/reception frequency band at −20 dB is 3.99 to 19.72 MHz.The group delay characteristics of the ultrasound probe having thetransmission/reception band characteristics of FIG. 3A is illustrated inFIG. 3B. As illustrated in FIG. 3B, the phase difference (delay amount)changes for each frequency, and the characteristics thereof is differentdepending on the characteristics of the ultrasound probe. In thisembodiment, it is important that a range of vibration in thetransmission/reception frequency band at −20 dB, at which transmissionand reception of the ultrasound are effectively performed, is small inthis group delay, namely, a difference (d) between the maximum value andthe minimum value of the group delay amounts is small. The smaller thedifference is, the more preferred the reception signal can be obtained,because cancellation hardly occur among a plurality of kinds of higherharmonic waves and an intended distance resolution can be obtained.Preferably, the difference between the maximum value and the minimumvalue is 0.15 radian or less.

Incidentally, also the group delay characteristics according to whichthe standard deviation in the transmission/reception frequency band at−20 dB is 0.025 or less can achieve the same effects.

The standard deviation of the group delays can be obtained, for example,by the following formula (1) indicating the standard deviation whensubject data is considered as a whole population.

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack\mspace{625mu}} & \; \\\sqrt{\frac{{\sum\left( {x - \overset{\_}{x}} \right)^{2}}\;}{n}} & (1)\end{matrix}$wherein x represents an average value of the subject data, and nrepresents the number of pieces of the subject data.

The granularity of data of the group delay characteristics forcalculation is preferably 200 points or more in thetransmission/reception frequency band at −20 dB of the ultrasound probeso as to enable obtaining reproducible results.

The group delay characteristics of the ultrasound probe 2 can becontrolled by appropriately changing parameters of components of theultrasound probe 2. For example, the frequency characteristics and/orthe group delay characteristics of the ultrasound probe 2 can beadjusted by appropriately setting characteristics of piezoelectricmaterial applied to the oscillators 2A, damping performance and/oracoustic reflection performance of backing material composing thebacking layer, the number of sheets of the acoustic matching materialcomposing the acoustic matching layer, acoustic impedance and thicknessof the acoustic matching material, etc. Also filler filled between theoscillators 2A, through which the ultrasound does not pass directly, hasinfluence on an unwanted vibration mode, and consequently the groupdelay characteristics of the oscillators 2A. Accordingly, changing ofparameters related to the filler and/or a manufacturing process of theultrasound probe 2 may be adjustment elements for controlling the groupdelay characteristics. Therefore, the ultrasound probe 2 having variouscharacteristics can be produced by a comprehensive adjustment.

The ultrasound image diagnosis apparatus body 1 is equipped with, forexample, an operation input section 11, transmission section 12,reception section 13, image generating section 14, image processingsection 15, Digital Scan Converter (DSC) 16, display section 17 andcontrol section 18, as illustrated in FIG. 2.

The operation input section 11 is composed of various switches, buttons,track ball, mouse, keyboard, etc. for inputting data such as a commandto instruct to start the diagnosis and personal information of the testobject, and outputs operation signals to the control section 18.

The transmission section 12 is a circuit which supplies the electricaldriving signal to the ultrasound probe 2 via the cable 3 according tothe control of the control section 18 so as to cause the ultrasoundprobe 2 to generate the transmission ultrasound. More specifically, asillustrated in FIG. 4, the transmission section 12 is equipped with aclock generating circuit 121, pulse generating circuit 122, duty settingsection 123 and delay circuit 124.

The clock generating circuit 121 is a circuit which generates a clocksignal determining the transmitting timing and/or transmission frequencyof the driving signal.

The pulse generating circuit 122 is a circuit which generates a pulsesignal as the driving signal at a predetermined cycle. As illustrated inFIG. 5, the pulse generating circuit 122 switches a voltage among fivevalues (+HV/+MV/0/−MV/−HV) to output the switched voltage, and therebythe pulse signal of rectangular wave is generated. The amplitude inpositive polarity of the pulse signal is same as that in negativepolarity in this example, but the amplitude is not limited to that. Thisembodiment switches the voltage among the five values to output theswitched voltage, but the number of the values is not limited to fiveand can be set to an appropriate value. Preferably, the number of thevalues is five or less. This can improve flexibility of a control offrequency components at low costs, and thereby higher resolutiontransmission ultrasound can be obtained.

The duty setting section 123 sets a duty ratio of the pulse signaloutput from the pulse generating circuit 122. Concretely, the pulsegenerating circuit 122 outputs the pulse signal of the pulse waveformaccording to the duty ratio set by the duty setting section 123. Theduty radio can be changed, for example, by an input operation in theoperation input section 11.

In this embodiment, the duty ratio of the pulse signal is preferably setso that peaks included in the transmission/reception frequency band ofthe ultrasound probe 2 occur on low frequency side and on high frequencyside with respect to the center frequency of the transmission/receptionfrequency band of the ultrasound probe 2. More preferably, the dutysetting section 123 sets the duty ratio of the pulse signal so that thesensitivity in the transmission/reception frequency band at −20 dB ofthe ultrasound probe 2 becomes −20 dB or more.

More detailed descriptions will be given with reference to FIGS. 6A, 6B,6C and 6D. FIG. 6A illustrates an example of transmission/reception bandcharacteristics Pr of the ultrasound probe. FIG. 6B illustrates anexample of the driving waveform of the pulse signal output from thetransmission section 12. FIG. 6C illustrates a frequency power spectrumobtained by a frequency analysis (FFT) of the driving waveform of thepulse signal of FIG. 6B. FIG. 6D illustrates the result of the frequencyanalysis (FFT) of the transmission ultrasound output from the ultrasoundprobe.

For example, the ultrasound probe of FIG. 6A has a peak frequency of14.2 MHz, a lower limit frequency (FL20) at −20 dB of 3.4 MHz, an upperlimit frequency (FH20) at −20 dB of 21.2 MHz, a center frequency at −20dB (FC20) of 12.3 MHz and a fractional bandwidth at −20 dB of 145%.

To this ultrasound probe, for example, a pulse signal Sg having thedriving waveform of FIG. 6B is applied. The pulse signal Sg is composedof a rectangular wave, and can be generated by switching the voltageamong the five values. As illustrated in FIG. 6C, the frequency powerspectrum, which is obtained by the frequency analysis of the drivingwaveform of the pulse signal Sg, has one (1) intensity peak (PK1: 5.8MHz) on the low frequency side and two intensity peaks (PK2: 13.2 MHz,PK3: 19.2 MHz) on the high frequency side with respect to the centerfrequency (FC20) in the transmission frequency band at −20 dB of theultrasound probe (the analysis result is indicated by “Sf” in FIG. 6C).In other words, when the pulse signal having the driving waveform ofFIG. 6B is applied to the ultrasound probe having the characteristics ofFIG. 6A, the peaks (PK1 to PK3) included in the transmission/receptionfrequency band of the ultrasound probe appear on the low frequency sideand on the high frequency side with respect to the center frequency(FC20) in the transmission/reception frequency band (FL20 to FH20) ofthe ultrasound probe. At that time, the intensities (P1: 3.8 dB, P2: 2.0dB, P3: 1.4 dB) at the respective intensity peaks are larger than theintensity (1.1 dB) of the frequency component of the frequency (12.3MHz) same as the center frequency in the transmission/receptionfrequency band of the ultrasound probe. Each of intensities in thefrequency regions between the adjacent intensity peaks is −20 dB or moreon the basis of the intensity at PK1 which is the maximum value amongthe intensities of the intensity peaks. As a result, the transmissionultrasound having the characteristics illustrated in FIG. 6D is outputfrom the ultrasound probe.

The transmission/reception band characteristics of the ultrasound probe2 and/or the driving waveform of the pulse signal according to thisembodiment is not limited to the above, and can be arbitrary set withinthe scope in which the present invention can be executed.

This embodiment outputs the pulse signal which has two intensity peakson the high frequency side with respect to the center frequency (FC20)in the transmission/reception frequency band of the ultrasound probe 2.Alternatively, the pulse signal may have three or more intensity peaks.By making the pulse signal have two or more intensity peaks on the highfrequency side with respect to the center frequency (FC20) in thetransmission/reception frequency band of the ultrasound probe 2, itbecomes possible to output the pulse signal having wider band on thehigh frequency side. Alternatively, the pulse signal may have only one(1) intensity peak on the high frequency side with respect to the centerfrequency (FC20) in the transmission/reception frequency band of theultrasound probe 2.

The delay circuit 124 is a circuit which sets a delay time to atransmission timing of the driving signal for each of individual pathscorresponding to the oscillators so as to delay transmission of thedriving signal by the set delay time so that transmission beams composedof transmission ultrasounds are focused.

The transmission section 12 having the above configuration sequentiallyswitches the oscillators 2A to which the driving signals are supplied,respectively, while shifting the oscillators 2A by a predeterminednumber every time the ultrasound is transmitted/received according tothe control of the control section 18, and performs scanning bysupplying the driving signals to the oscillators 2A whose outputs areselected.

In this embodiment, the transmission section 12 is configured to outputthe pulse signal of the driving waveform having the group delaycharacteristics according to which the difference between the maximumvalue and the minimum value is 0.15 radian or less in the frequency bandwhere the frequency band contained in the transmission/receptionfrequency band at −20 dB of the ultrasound probe 2 and the frequencyband at −20 dB of the driving waveform in the pulse signal overlap eachother. In this embodiment, the phase component for each frequency at thetime of performing the frequency analysis of the driving waveform isconsidered as the response delay, and the obtained calculation result isregarded as the group delay characteristics of the driving waveform.

Specifically, for example, when the frequency analysis of the drivingwaveform of FIG. 7A is performed, the power spectrum illustrated in FIG.7B is obtained. The group delay characteristics of the driving waveformof FIG. 7A becomes that illustrated in FIG. 7C. The frequency band at−20 dB of this driving waveform was within a range from the lower limitfrequency (FL20 (V)) to the upper limit frequency (FH20 (V)), asillustrated in FIG. 7B. When the pulse signal having such drivingwaveform is applied to the ultrasound probe having thetransmission/reception band characteristics of FIG. 3A, it is importantthat the difference (d) between the maximum value and the minimum valueof the group delay amounts in the frequency band where the frequencyband (the range from the lower limit frequency (FL20 (P)) to the upperlimit frequency (FH20 (P)), namely, 3.99 to 19.72 MHz in thisembodiment) contained in the transmission/reception frequency band at−20 dB of the ultrasound probe and the frequency band (the range fromthe lower limit frequency (FL20 (V)) to the upper limit frequency (FH20(V))) at −20 dB of the driving waveform illustrated in FIG. 7B overlapeach other. The smaller the difference is, the more preferable theobtained reception signal is, because cancellation among the multiplekinds of the higher harmonic waves hardly occurs and an intendeddistance resolution can be obtained. Preferably, the difference betweenthe maximum value and the minimum value is 0.15 radian or less. In theabove case, the frequency band where the frequency band contained in thetransmission/reception frequency band at −20 dB of the ultrasound probeand the frequency band at −20 dB of the driving waveform overlap eachother corresponds to the frequency band contained in thetransmission/reception frequency band at −20 dB of the ultrasound probe.Therefore, the difference (d) between the maximum value and the minimumvalue of the group delay amounts within this range is preferably smallas much as possible.

The group delay characteristics can be controlled by appropriatelychanging the driving waveform. It may be group delay characteristicsaccording to which the standard deviation in the frequency band wherethe frequency band contained in the transmission/reception frequencyband at −20 dB of the ultrasound probe 2 and the frequency band at −20dB of the pulse signal overlap each other is 0.025 or less. The standarddeviation can be obtained by the above-described method.

In this embodiment, more preferably, the ultrasound probe 2 and thedriving waveform are set so that the difference between the maximumvalue and the minimum value of the group delays is 0.15 radian or less,the group delays being obtained by totaling the group delay of theultrasound probe 2 obtained as described above and the group delay ofthe driving waveform in the pulse signal to be given to the ultrasoundprobe 2, in the frequency band where the frequency band contained in thetransmission/reception frequency band at −20 dB of the ultrasound probe2 and the frequency band at −20 dB of the driving waveform in the pulsesignal overlap each other. Incidentally, at least one of the group delaycharacteristics of the ultrasound probe 2 and of the driving waveformdoes not have to meet the above-described condition, as long as thetotalized group delay meets the above-described condition.

Incidentally, in the case of outputting the pulse signal of the drivingwaveform in which the frequency bandwidth where the frequency bandcontained in the transmission/reception frequency band at −20 dB of theultrasound probe 2 and the frequency band at −20 dB of the drivingwaveform of the pulse signal overlap each other covers 70% or more ofthe frequency bandwidth at −20 dB of the ultrasound probe 2, thebroadband ultrasound can be transmitted/received, and accordingly theeffects of the present invention can be suitably obtained. According tothe above-described condition, the frequency bandwidth where thefrequency band contained in the transmission/reception frequency band at−20 dB of the ultrasound probe 2 and the frequency band at −20 dB of thedriving waveform in the pulse signal overlap each other covers 100% ofthe frequency bandwidth at −20 dB of the ultrasound probe 2, andtherefore the excellent broadband ultrasound can betransmitted/received.

In this embodiment, the driving waveform of the pulse signal to beoutput is made as the driving waveform of the period of 1.5 or more,which can scatter the output voltage of the pulse signal in a time axisdirection. As a result, the maximum output voltage can be made small,and the costs can be reduced. Alternatively, the period of the drivingwaveform may be less than 1.5.

In this embodiment, the pulse duration of the pulse signal to be outputis preferably set to the time corresponding to two period at the centerfrequency of the transmission/reception frequency band at −20 dB of theultrasound probe 2 or more, which can scatter the output voltage of thepulse signal in the time axis direction. FIG. 8 illustrates arelationship between the frequency and the time corresponding to twoperiod of the frequency. In this embodiment, preferably the pulseduration is set to be equal to or more than the time represented ascurve H in FIG. 8H. For example, since the center frequency (FC20) inthe transmission/reception frequency band at −20 dB of the ultrasoundprobe 2 having the transmission/reception band characteristics of FIG.3A is 11.86 MHz, the pulse duration is preferably set to be equal ormore than time T corresponding to this value. Alternatively, the pulseduration may be set to be less than the time corresponding to two periodat the center frequency in the transmission/reception frequency band at−20 dB of the ultrasound probe 2.

This embodiment can execute the pulse inversion method to extract higherharmonic components to be described later. Concretely, when executingthe pulse inversion method, the transmission section 12 can transmit thefirst pulse signal, and the second pulse signal obtained by invertingthe polarity of the first pulse signal, to the same scanning line with apredetermined time interval. At that time, the transmission section 12may transmit the second pulse signal obtained by inverting the polarityof the first pulse signal by making at least one of duty ratiosdifferent from other duty ratios of the first pulse signal, the secondpulse signal having an asymmetric relationship with the first pulsesignal. The asymmetric relationship between the waveforms means that onewaveform is not linearly symmetrical, and is not symmetrical about apoint, with another waveform. In other words, it means that a shape ofone waveform does not match (is not symmetrical) a shape of anotherwaveform even when the one waveform is subjected to time reversal orpolarity inversion. The second pulse signal can be obtained also bymaking the first pulse signal subjected to time reversal. Thus, thetransmission section 12 of this embodiment can output the pulse signalshaving different driving waveforms to the same scanning line with apredetermined time interval multiple times.

As illustrated in FIG. 2, the reception section 13 is a circuit whichreceives the electrical reception signals from the ultrasound probe 2via the cable 3 according to the control by the control section 18. Thereception section 13 is equipped with, for example, an amplifier, an A/Dconverting circuit and a phase regulating adder circuit. The amplifieris a circuit to amplify the reception signal at a predeterminedamplification factor that is previously set, for each of the individualpaths corresponding to the respective oscillators 2A. The A/D convertingcircuit is a circuit to make the amplified reception signal subjected toAnalog/Digital (A/D) conversion. The phase regulating adder circuit is acircuit to apply the delay time to the reception signal subjected to theA/D conversion, for each of the individual paths corresponding to therespective oscillators 2A, to regulate the time phase, and adds (phasingaddition) these reception signals to generate sound ray data.

The image generating section 14 performs an envelope detectionprocessing and/or logarithmic amplification to the sound ray data outputfrom the reception section 13, and performs luminance conversion by gainadjustment or the like, so as to generate B mode image data. Thus, the Bmode image data represents the intensity of the reception signal withluminance. The B mode image data generated in the image generatingsection 14 is transmitted to the image processing section 15. The imagegenerating section 14 is also equipped with a higher harmonic componentextracting section 14A.

The higher harmonic component extracting section 14A extracts the higherharmonic components from the reception signal output from the receptionsection 13 by executing the pulse inversion method. In this embodiment,the higher harmonic component extracting section 14A extracts the higherharmonic components including mainly the secondary higher harmonic wave.The secondary higher harmonic components can be extracted by adding(totaling) the reception signals obtained from the reflected ultrasoundscorresponding to two transmission ultrasounds, respectively, generatedfrom the above-described first pulse signal and the second pulse signal,removing the basic wave components contained in the reception signals,and performing a filter processing.

The image processing section 15 is equipped with an image memory section15A composed of a semiconductor memory such as a Dynamic Random AccessMemory (DRAM). The image processing section 15 stores the B mode imagedata output from the image generating section 14 in a unit of frames inthe image memory section 15A. The image data in the frame unit aresometimes referred to as ultrasound image data or frame image data. Theimage processing section 15 suitably reads out the ultrasound image datastored in the image memory section 15A to output the ultrasound imagedata to the DSC 16.

The DSC 16 converts the ultrasound image data received from the imageprocessing section 15 into an image signal in a scanning system of atelevision signal, and outputs the image signal to the display section17.

The display section 17 may be a display device such as a Liquid CrystalDisplay (LCD), Cathode-Ray Tube (CRT) display, organic ElectronicLuminescence (EL) display, inorganic EL display and plasma display. Thedisplay section 17 displays the ultrasound image on a display screenaccording to the image signal output from the DSC 16.

The control section 18 is equipped with, for example, a CentralProcessing Unit (CPU), Read Only Memory (ROM) and Random Access Memory(RAM), and reads out the various processing programs such as a systemprogram stored in the ROM to expand the programs in the RAM, andcentrally controls the sections of the ultrasound image diagnosisapparatus S according to the expanded programs.

The ROM is composed of, for example, a nonvolatile memory such assemiconductor, and stores the system program applicable for theultrasound image diagnosis apparatus S, various processing programsexecutable on the system program, and various pieces of data. Theseprograms are stored in the form of program codes readable by thecomputers, and the CPU successively executes the operations according tothe program codes.

The RAM forms a work area in which various programs executed by the CPUand data related to these programs are temporarily stored.

EXAMPLES

Hereinafter examples of the present invention will be described in moredetail. It is needless to say that the present invention is not limitedto these examples.

First, ultrasound probes A to D used in the examples and comparativeexamples as the ultrasound probes 2 will be described.

<Ultrasound Probe A>

The ultrasound probe A having characteristics illustrated in FIGS. 9A,9B and 9C was used. FIG. 9A illustrates impulse response characteristicsat the time when an impulse signal was given to the ultrasound probe A,FIG. 9B illustrates the transmission/reception band characteristics ofthe ultrasound probe A, and FIG. 9C illustrates the group delaycharacteristics obtained from a phase difference, for each frequency,between the impulse signal given to the ultrasound probe A and thereception signal obtained as a result of the transmission/reception ofthe ultrasound executed by the impulse signal. In FIG. 9A, thehorizontal axis indicates the time, and the vertical axis indicates thevoltage. In FIG. 9B, the horizontal axis indicates the frequency, andthe vertical axis indicates the sensitivity. In FIG. 9C, the horizontalaxis indicates the frequency, and the vertical axis indicates the groupdelay amount.

The group delay characteristics was measured while a plate for makingthe ultrasound from the ultrasound probe reflected thereon was installedunderwater so that the surface of the plate was perpendicular to theultrasound probe. The plate was placed at a position of so-called FlatPlate Focus, namely, at a position where the maximum value of theintensity of the ultrasound can be obtained because the ultrasounds wereconverged at the position by the acoustic lens included in theultrasound probe. The impulse signal given to the ultrasound probe wasan impulse signal having a substantially flat frequency characteristicsand a substantially flat group delay characteristics. One (1) element ofthe ultrasound probe was driven by an Olympus Model 5900PR pulserreceiver in a transmission mode of 1 uJ, a frequency analysis wasperformed to the electrical reception signal at the time when theultrasound was transmitted/received to/from the SUS plate placed at theFlat Plate Focus position in a degassed water so as to obtain the phasecharacteristics, and the phase characteristics was differentiated so asto obtain the group delay characteristics. The same measurements of thegroup delay characteristics were performed also to the ultrasound probesto be described later.

As illustrated in FIG. 9B, according to the transmission/reception bandcharacteristics of the ultrasound probe A, the lower limit frequency(FL20) was 3.99 MHz, the upper limit frequency (FH20) was 19.72 MHz, thecenter frequency (FC20) was 11.86 MHz, and the fractional bandwidth at−20 dB of transmission/reception was 133%. The difference between themaximum value and the minimum value of the group delay amounts in thetransmission/reception bandwidth (FL20: 3.99 MHz to FH20: 19.72 MHz) at−20 dB of the ultrasound probe A was 0.082, and the standard deviationof the group delay amounts in this transmission/reception bandwidth was0.0184.

<Ultrasound Probe B>

The ultrasound probe B having characteristics illustrated in FIGS. 10A,10B and 10C was used. FIG. 10A illustrates an impulse responsecharacteristics at the time when an impulse signal was given to theultrasound probe B, FIG. 10B illustrates the transmission/reception bandcharacteristics of the ultrasound probe B, and FIG. 10C illustrates thegroup delay characteristics obtained from a phase difference, for eachfrequency, between the impulse signal given to the ultrasound probe Band the reception signal obtained as a result of thetransmission/reception of the ultrasound executed by the impulse signal.In FIG. 10A, the horizontal axis indicates the time, and the verticalaxis indicates the voltage. In FIG. 10B, the horizontal axis indicatesthe frequency, and the vertical axis indicates the sensitivity. In FIG.10C, the horizontal axis indicates the frequency, and the vertical axisindicates the group delay amount.

As illustrated in FIG. 10B, according to the transmission/reception bandcharacteristics of the ultrasound probe B, the lower limit frequency(FL20) was 3.82 MHz, the upper limit frequency (FH20) was 19.86 MHz, thecenter frequency (FC20) was 11.84 MHz, and the fractional bandwidth at−20 dB of the transmission/reception was 135%. The difference betweenthe maximum value and the minimum value of the group delay amounts inthe transmission/reception bandwidth (FL20: 3.82 MHz to FH20: 19.86 MHz)at −20 dB of the ultrasound probe B was 0.082, and the standarddeviation of the group delay amounts in this transmission/receptionbandwidth was 0.0198.

<Ultrasound Probe C>

The ultrasound probe C having characteristics illustrated in FIGS. 11A,11B and 11C was used. FIG. 11A illustrates an impulse responsecharacteristics at the time when an impulse signal was given to theultrasound probe C, FIG. 11B illustrates the transmission/reception bandcharacteristics of the ultrasound probe C, and FIG. 11C illustrates thegroup delay characteristics obtained from a phase difference, for eachfrequency, between the impulse signal given to the ultrasound probe Cand the reception signal obtained as a result of thetransmission/reception of the ultrasound executed by the impulse signal.In FIG. 11A, the horizontal axis indicates the time, and the verticalaxis indicates the voltage. In FIG. 11B, the horizontal axis indicatesthe frequency, and the vertical axis indicates the sensitivity. In FIG.11C, the horizontal axis indicates the frequency, and the vertical axisindicates the group delay amount.

As illustrated in FIG. 11B, according to the transmission/reception bandcharacteristics of the ultrasound probe C, the lower limit frequency(FL20) was 3.75 MHz, the upper limit frequency (FH20) was 20.23 MHz, thecenter frequency (FC20) was 11.99 MHz, and the fractional bandwidth at−20 dB of the transmission/reception was 137%. The difference betweenthe maximum value and the minimum value of the group delay amounts inthe transmission/reception bandwidth (FL20: 3.75 MHz to FH20: 20.23 MHz)at −20 dB of the ultrasound probe C was 0.154, and the standarddeviation of the group delay amounts in this transmission/receptionbandwidth was 0.0287.

<Ultrasound Probe D>

The ultrasound probe D having characteristics illustrated in FIGS. 12A,12B and 12C was used. FIG. 12A illustrates an impulse responsecharacteristics at the time when an impulse signal was given to theultrasound probe D, FIG. 12B illustrates the transmission/reception bandcharacteristics of the ultrasound probe D, and FIG. 12C illustrates thegroup delay characteristics obtained from a phase difference, for eachfrequency, between the impulse signal given to the ultrasound probe Dand the reception signal obtained as a result of thetransmission/reception of the ultrasound executed by the impulse signal.In FIG. 12A, the horizontal axis indicates the time, and the verticalaxis indicates the voltage. In FIG. 12B, the horizontal axis indicatesthe frequency, and the vertical axis indicates the sensitivity. In FIG.12C, the horizontal axis indicates the frequency, and the vertical axisindicates the group delay amount.

As illustrated in FIG. 12B, according to the transmission/reception bandcharacteristics of the ultrasound probe D, the lower limit frequency(FL20) was 3.96 MHz, the upper limit frequency (FH20) was 19.78 MHz, thecenter frequency (FC20) was 11.87 MHz, and the fractional bandwidth at−20 dB of the transmission/reception was 133%. The difference betweenthe maximum value and the minimum value of the group delay amounts inthe transmission/reception bandwidth (FL20: 3.96 MHz to FH20: 19.78 MHz)at −20 dB of the ultrasound probe D was 0.200, and the standarddeviation of the group delay amounts in this transmission/receptionbandwidth was 0.0301.

Example 1

The above-described ultrasound probe A was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform A illustrated in FIG. 13A. FIG.13B illustrates the frequency power spectrum obtained by the frequencyanalysis of the driving waveform A. FIG. 13C illustrates the group delaycharacteristics of the driving waveform A. In FIG. 13A, the horizontalaxis indicates the time, and the vertical axis indicates the voltage. InFIG. 13B, the horizontal axis indicates the frequency, and the verticalaxis indicates the signal intensity. In FIG. 13C, the horizontal axisindicates the frequency, and the vertical axis indicates the group delayamount.

The group delay characteristics was measured by measuring a voltagewaveform at the time when a probe receptacle included in the ultrasoundimage diagnosis apparatus body was terminated with a resistance of 50Ωand driven, then performing the frequency analysis to this voltagewaveform to obtain the phase characteristics, and differentiating thephase characteristics. The same measurements of the group delaycharacteristics were performed to the driving waveforms to be describedlater.

The driving waveform A had three intensity peaks in thetransmission/reception frequency band (3.99 MHz to 19.72 MHz) at −20 dBof the ultrasound probe A, and one of the intensity peaks located on thelow frequency side with respect to the center frequency (FC20: 11.86MHz) in the transmission/reception frequency band at −20 dB of theultrasound probe A, and other two intensity peaks located on the highfrequency side with respect to the center frequency (FC20: 11.86 MHz) inthe transmission/reception frequency band at −20 dB of the ultrasoundprobe A.

The pulse duration of the driving waveform A was 233 ns, whichcorresponded to 2.76 periods at the center frequency (FC20: 11.86 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe A. In other words, the pulse duration of the driving waveform Awas equal to or more than the time corresponding to two periods at thecenter frequency (FC20: 11.86 MHz) in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A (see FIG. 24).

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform A overlapeach other corresponds to the transmission/reception frequency band at−20 dB of the ultrasound probe A, which was within the range from thelower limit frequency of 3.99 MHz (FL20) to the upper limit frequency of19.72 MHz (FH20). A cover ratio of the ultrasound probe A of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 100%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform A in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe A and the frequency band at −20 dB of thedriving waveform A overlap each other was 0.107 radian. The standarddeviation of the group delays of the driving waveform A in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A and the frequencyband at −20 dB of the driving waveform A overlap each other was 0.0208.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe A obtained asdescribed above and the group delay of the driving waveform A, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform A overlapeach other, was 0.115. FIG. 21 illustrates the totaling result of thegroup delay of the ultrasound probe A and the group delay of the drivingwaveform A.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform A.

Example 2

The above-described ultrasound probe B was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform A same as that of Example 1.

The driving waveform A had three intensity peaks in thetransmission/reception frequency band (3.82 MHz to 19.86 MHz) at −20 dBof the ultrasound probe B, and one of the intensity peaks located on thelow frequency side with respect to the center frequency (FC20: 11.84MHz) in the transmission/reception frequency band at −20 dB of theultrasound probe B, and other two intensity peaks located on the highfrequency side with respect to the center frequency (FC20: 11.84 MHz) inthe transmission/reception frequency band at −20 dB of the ultrasoundprobe B.

The pulse duration of the driving waveform A was 233 ns, whichcorresponded to 2.76 periods at the center frequency (FC20: 11.84 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe B. In other words, the pulse duration of the driving waveform Awas equal to or more than the time corresponding to two periods at thecenter frequency (FC20: 11.84 MHz) in the transmission/receptionfrequency band at −20 dB of the ultrasound probe B (see FIG. 24).

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeB and the frequency band at −20 dB of the driving waveform A overlapeach other corresponds to the transmission/reception frequency band at−20 dB of the ultrasound probe B, which was within the range from thelower limit frequency of 3.82 MHz (FL20) to the upper limit frequency of19.86 MHz (FH20). A cover ratio of the ultrasound probe B of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 100%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform A in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe B and the frequency band at −20 dB of thedriving waveform A overlap each other was 0.107 radian. The standarddeviation of the group delays of the driving waveform A in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe B and the frequencyband at −20 dB of the driving waveform A overlap each other was 0.0208.

The difference between the maximum value and the minimum value of thetotaling value of the group delay of the ultrasound probe B obtained asdescribed above and the group delay of the driving waveform A, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeB and the frequency band at −20 dB of the driving waveform A overlapeach other, was 0.089.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform A.

Example 3

The above-described ultrasound probe A was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform A same as that of Example 1.

The second pulse signal was the driving signal of the driving waveform Cillustrated in FIG. 15A. FIG. 15B illustrates the frequency powerspectrum obtained by the frequency analysis of the driving waveform C.FIG. 15C illustrates the group delay characteristics of the drivingwaveform C. In FIG. 15A, the horizontal axis indicates the time, and thevertical axis indicates the voltage. In FIG. 15B, the horizontal axisindicates the frequency, and the vertical axis indicates the signalintensity. In FIG. 15C, the horizontal axis indicates the frequency, andthe vertical axis indicates the group delay amount.

The driving waveform C had two intensity peaks in thetransmission/reception frequency band (3.99 MHz to 19.72 MHz) at −20 dBof the ultrasound probe A. One intensity peak located on the lowfrequency side, and another intensity peak located on the high frequencyside, with respect to the center frequency (FC20: 11.86 MHz) in thetransmission/reception frequency band at −20 dB of the ultrasound probeA.

The driving waveform C was obtained by inverting the polarity of thedriving waveform A by partially changing the duty radios of the drivingwaveform thereof.

The pulse duration of the driving waveform C was 233 ns, whichcorresponded to 2.76 periods at the center frequency (FC20: 11.86 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe A. In other words, the pulse duration of the driving waveform Cwas equal to or more than the time corresponding to two periods at thecenter frequency (FC20: 11.86 MHz) in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A (see FIG. 24).

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform C overlapeach other was within the range from the lower limit frequency (FL20) of3.99 MHz to the upper limit frequency (FH20) of 16.13 MHz. Concretely,the above upper limit frequency was smaller than the upper limitfrequency in the transmission/reception frequency band at −20 dB of theultrasound probe A, whereas the above lower limit frequency correspondsto the lower limit frequency in the transmission/reception frequencyband at −20 dB of the ultrasound probe A. Thus, this frequency band isnarrower than the transmission frequency band at −20 dB of theultrasound probe A. A cover ratio of the ultrasound probe A of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 77%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform C in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe A and the frequency band at −20 dB of thedriving waveform C overlap each other was 0.079 radian. The standarddeviation of the group delays of the driving waveform C in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A and the frequencyband at −20 dB of the driving waveform C overlap each other was 0.0117.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe A obtained asdescribed above and the group delay of the driving waveform C, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform C overlapeach other, was 0.087.

Example 4

The above-described ultrasound probe A was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform B illustrated in FIG. 14A. FIG.14B illustrates the frequency power spectrum obtained by the frequencyanalysis of the driving waveform B. FIG. 14C illustrates the group delaycharacteristics of the driving waveform B. In FIG. 14A, the horizontalaxis indicates the time, and the vertical axis indicates the voltage. InFIG. 14B, the horizontal axis indicates the frequency, and the verticalaxis indicates the signal intensity. In FIG. 14C, the horizontal axisindicates the frequency, and the vertical axis indicates the group delayamount.

The driving waveform B had three intensity peaks in thetransmission/reception frequency band (3.99 MHz to 19.72 MHz) at −20 dBof the ultrasound probe A, and one of the intensity peaks located on thelow frequency side with respect to the center frequency (FC20: 11.86MHz) in the transmission/reception frequency band at −20 dB of theultrasound probe A, and other two intensity peaks located on the highfrequency side with respect to the center frequency (FC20: 11.86 MHz) inthe transmission/reception frequency band at −20 dB of the ultrasoundprobe A.

The pulse duration of the driving waveform B was 207 ns, whichcorresponded to 2.45 periods at the center frequency (FC20: 11.86 MHz)of the transmission/reception frequency band at −20 dB of the ultrasoundprobe A. In other words, the pulse duration of the driving waveform Bwas equal to or more than the time corresponding to two periods at thecenter frequency (FC20: 11.86 MHz) of the transmission/receptionfrequency band at −20 dB of the ultrasound probe A (see FIG. 24).

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform B overlapeach other corresponds to the transmission/reception frequency band at−20 dB of the ultrasound probe A, which was within the range from thelower limit frequency of 3.99 MHz (FL20) to the upper limit frequency of19.72 MHz (FH20). A cover ratio of the ultrasound probe A of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 100%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform B in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe A and the frequency band at −20 dB of thedriving waveform B overlap each other was 0.092 radian. The standarddeviation of the group delays of the driving waveform B in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A and the frequencyband at −20 dB of the driving waveform B overlap each other was 0.0195.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe A obtained asdescribed above and the group delay of the driving waveform B, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform B overlapeach other, was 0.120.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform B.

Example 5

The above-described ultrasound probe A was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform C described by referring to FIGS.15A, 15B and 15C.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform C.

Example 6

The above-described ultrasound probe A was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform D illustrated in FIG. 16A. FIG.16B illustrates the frequency power spectrum obtained by the frequencyanalysis of the driving waveform D. FIG. 16C illustrates the group delaycharacteristics of the driving waveform D. In FIG. 16A, the horizontalaxis indicates the time, and the vertical axis indicates the voltage. InFIG. 16B, the horizontal axis indicates the frequency, and the verticalaxis indicates the signal intensity. In FIG. 16C, the horizontal axisindicates the frequency, and the vertical axis indicates the group delayamount.

The driving waveform D had two intensity peaks in thetransmission/reception frequency band (3.99 MHz to 19.72 MHz) at −20 dBof the ultrasound probe A. One intensity peak located on the lowfrequency side, and another intensity peak located on the high frequencyside, with respect to the center frequency (FC20: 11.86 MHz) in thetransmission/reception frequency band at −20 dB of the ultrasound probeA.

The pulse duration of the driving waveform D was 180 ns, whichcorresponded to 2.13 periods at the center frequency (FC20: 11.86 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe A. In other words, the pulse duration of the driving waveform Dwas equal to or more than the time corresponding to two periods at thecenter frequency (FC20: 11.86 MHz) of the transmission/receptionfrequency band at −20 dB of the ultrasound probe A (see FIG. 24).

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform D overlapeach other was within the range from the lower limit frequency (FL20) of3.99 MHz to the upper limit frequency (FH20) of 17.02 MHz. Concretely,the above upper limit frequency was smaller than the upper limitfrequency of the transmission/reception frequency band at −20 dB of theultrasound probe A, whereas the above lower limit frequency correspondsto the lower limit frequency of the transmission/reception frequencyband at −20 dB of the ultrasound probe A. Thus, this frequency band isnarrower than the transmission frequency band at −20 dB of theultrasound probe A. A cover ratio of the ultrasound probe A of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 83%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform D in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe A and the frequency band at −20 dB of thedriving waveform D overlap each other was 0.065 radian. The standarddeviation of the group delays of the driving waveform D in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A and the frequencyband at −20 dB of the driving waveform D overlap each other was 0.0130.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe A obtained asdescribed above and the group delay of the driving waveform D, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform D overlapeach other, was 0.089.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform D.

Example 7

The above-described ultrasound probe A was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform E illustrated in FIG. 17A. FIG.17B illustrates the frequency power spectrum obtained by the frequencyanalysis of the driving waveform E. FIG. 17C illustrates the group delaycharacteristics of the driving waveform E. In FIG. 17A, the horizontalaxis indicates the time, and the vertical axis indicates the voltage. InFIG. 17B, the horizontal axis indicates the frequency, and the verticalaxis indicates the signal intensity. In FIG. 17C, the horizontal axisindicates the frequency, and the vertical axis indicates the group delayamount.

The driving waveform E had two intensity peaks in thetransmission/reception frequency band (3.99 MHz to 19.72 MHz) at −20 dBof the ultrasound probe A. One intensity peak located on the lowfrequency side, and another intensity peak located on the high frequencyside, with respect to the center frequency (FC20: 11.86 MHz) in thetransmission/reception frequency band at −20 dB of the ultrasound probeA.

The pulse duration of the driving waveform E was 180 ns, whichcorresponded to 2.13 periods at the center frequency (FC20: 11.86 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe A. In other words, the pulse duration of the driving waveform Ewas equal to or more than the time corresponding to two periods at thecenter frequency (FC20: 11.86 MHz) in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A (see FIG. 24).

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform E overlapeach other was within the range from the lower limit frequency (FL20) of3.99 MHz to the upper limit frequency (FH20) of 16.88 MHz. Concretely,the above upper limit frequency was smaller than the upper limitfrequency of the transmission/reception frequency band at −20 dB of theultrasound probe A, whereas the above lower limit frequency correspondsto the lower limit frequency of the transmission/reception frequencyband at −20 dB of the ultrasound probe A. Thus, this frequency band isnarrower than the transmission frequency band at −20 dB of theultrasound probe A. A cover ratio of the ultrasound probe A of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 82%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform E in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe A and the frequency band at −20 dB of thedriving waveform E overlap each other was 0.086 radian. The standarddeviation of the group delays of the driving waveform E in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A and the frequencyband at −20 dB of the driving waveform E overlap each other was 0.0149.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe A obtained asdescribed above and the group delay of the driving waveform E, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform E overlapeach other, was 0.127.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform E.

Example 8

The above-described ultrasound probe B was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform B described by referring to FIGS.14A, 14B and 14C.

The driving waveform B had three intensity peaks in thetransmission/reception frequency band (3.82 MHz to 19.86 MHz) at −20 dBof the ultrasound probe B, and one of the intensity peaks located on thelow frequency side with respect to the center frequency (FC20: 11.84MHz) in the transmission/reception frequency band at −20 dB of theultrasound probe B, and other two intensity peaks located on the highfrequency side with respect to the center frequency (FC20: 11.84 MHz) inthe transmission/reception frequency band at −20 dB of the ultrasoundprobe B.

The pulse duration of the driving waveform B was 207 ns, whichcorresponded to 2.45 periods at the center frequency (FC20: 11.84 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe B. In other words, the pulse duration of the driving waveform Bwas equal to or more than the time corresponding to two periods at thecenter frequency (FC20: 11.84 MHz) in the transmission/receptionfrequency band at −20 dB of the ultrasound probe B (see FIG. 24).

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeB and the frequency band at −20 dB of the driving waveform B overlapeach other corresponds to the transmission/reception frequency band at−20 dB of the ultrasound probe B, which was within the range from thelower limit frequency of 3.82 MHz (FL20) to the upper limit frequency of19.86 MHz (FH20). A cover ratio of the ultrasound probe B of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 100%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform B in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe B and the frequency band at −20 dB of thedriving waveform B overlap each other was 0.092 radian. The standarddeviation of the group delays of the driving waveform B in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe B and the frequencyband at −20 dB of the driving waveform B overlap each other was 0.0194.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe B obtained asdescribed above and the group delay of the driving waveform B, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeB and the frequency band at −20 dB of the driving waveform B overlapeach other, was 0.134. FIG. 22 illustrates the totaling result of thegroup delay of the ultrasound probe B and the group delay of the drivingwaveform B.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform B.

Example 9

The above-described ultrasound probe B was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform D described by referring to FIGS.16A, 16B and 16C.

The driving waveform D had two intensity peaks in thetransmission/reception frequency band (3.82 MHz to 19.86 MHz) at −20 dBof the ultrasound probe B. One intensity peak located on the lowfrequency side, and another intensity peak located on the high frequencyside, with respect to the center frequency (FC20: 11.84 MHz) in thetransmission/reception frequency band at −20 dB of the ultrasound probeB.

The pulse duration of the driving waveform D was 180 ns, whichcorresponded to 2.13 periods at the center frequency (FC20: 11.84 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe B. In other words, the pulse duration of the driving waveform Dwas equal to or more than the time corresponding to two periods at thecenter frequency (FC20: 11.84 MHz) in the transmission/receptionfrequency band at −20 dB of the ultrasound probe B (see FIG. 24).

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeB and the frequency band at −20 dB of the driving waveform D overlapeach other was within the range from the lower limit frequency (FL20) of3.82 MHz to the upper limit frequency (FH20) of 17.02 MHz. Concretely,the above upper limit frequency was smaller than the upper limitfrequency of the transmission/reception frequency band at −20 dB of theultrasound probe B, whereas the above lower limit frequency correspondsto the lower limit frequency of the transmission/reception frequencyband at −20 dB of the ultrasound probe B. Thus, this frequency band isnarrower than the transmission frequency band at −20 dB of theultrasound probe B. A cover ratio of the ultrasound probe B of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 82%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform D in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe B and the frequency band at −20 dB of thedriving waveform D overlap each other was 0.065 radian. The standarddeviation of the group delays of the driving waveform D in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe B and the frequencyband at −20 dB of the driving waveform D overlap each other was 0.0131.

The difference between the maximum value and the minimum value of thetotaling value of the group delay of the ultrasound probe B obtained asdescribed above and the group delay of the driving waveform D, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeB and the frequency band at −20 dB of the driving waveform D overlapeach other, was 0.076.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform D.

Comparative Example 1

The above-described ultrasound probe C was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform A same as that of Example 1.

The driving waveform A had three intensity peaks in thetransmission/reception frequency band (3.75 MHz to 20.23 MHz) at −20 dBof the ultrasound probe C, and one of the intensity peaks located on thelow frequency side with respect to the center frequency (FC20: 11.99MHz) in the transmission/reception frequency band at −20 dB of theultrasound probe C, and other two intensity peaks located on the highfrequency side with respect to the center frequency (FC20: 11.99 MHz) inthe transmission/reception frequency band at −20 dB of the ultrasoundprobe C.

The pulse duration of the driving waveform A was 233 ns, whichcorresponded to 2.79 periods at the center frequency (FC20: 11.99 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe C.

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeC and the frequency band at −20 dB of the driving waveform A overlapeach other corresponds to the transmission/reception frequency band at−20 dB of the ultrasound probe C, which was within the range from thelower limit frequency of 3.75 MHz (FL20) to the upper limit frequency of20.23 MHz (FH20). A cover ratio of the ultrasound probe C of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 100%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform A in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe C and the frequency band at −20 dB of thedriving waveform A overlap each other was 0.107 radian. The standarddeviation of the group delays of the driving waveform A in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe C and the frequencyband at −20 dB of the driving waveform A overlap each other was 0.0206.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe C obtained asdescribed above and the group delay of the driving waveform A, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeC and the frequency band at −20 dB of the driving waveform A overlapeach other, was 0.152.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform A.

Comparative Example 2

The above-described ultrasound probe D was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform A same as that of Example 1.

The driving waveform A had three intensity peaks in thetransmission/reception frequency band (3.96 MHz to 19.78 MHz) at −20 dBof the ultrasound probe D, and one of the intensity peaks located on thelow frequency side with respect to the center frequency (FC20: 11.87MHz) in the transmission/reception frequency band at −20 dB of theultrasound probe D, and other two intensity peaks located on the highfrequency side with respect to the center frequency (FC20: 11.87 MHz) inthe transmission/reception frequency band at −20 dB of the ultrasoundprobe D.

The pulse duration of the driving waveform A was 233 ns, whichcorresponded to 2.77 periods at the center frequency (FC20: 11.87 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe D.

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeD and the frequency band at −20 dB of the driving waveform A overlapeach other corresponds to the transmission/reception frequency band at−20 dB of the ultrasound probe D, which was within the range from thelower limit frequency of 3.96 MHz (FL20) to the upper limit frequency of19.78 MHz (FH20). A cover ratio of the ultrasound probe D of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 100%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform A in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe D and the frequency band at −20 dB of thedriving waveform A overlap each other was 0.107 radian. The standarddeviation of the group delays of the driving waveform A in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe D and the frequencyband at −20 dB of the driving waveform A overlap each other was 0.0208.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe D obtained asdescribed above and the group delay of the driving waveform A, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeD and the frequency band at −20 dB of the driving waveform A overlapeach other, was 0.163.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform A.

Comparative Example 3

The above-described ultrasound probe A was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform F illustrated in FIG. 18A. FIG.18B illustrates the frequency power spectrum obtained by the frequencyanalysis of the driving waveform F. FIG. 18C illustrates the group delaycharacteristics of the driving waveform F. In FIG. 18A, the horizontalaxis indicates the time, and the vertical axis indicates the voltage. InFIG. 18B, the horizontal axis indicates the frequency, and the verticalaxis indicates the signal intensity. In FIG. 18C, the horizontal axisindicates the frequency, and the vertical axis indicates the group delayamount.

The driving waveform F had three intensity peaks in thetransmission/reception frequency band (3.99 MHz to 19.72 MHz) at −20 dBof the ultrasound probe A, and one of the intensity peaks located on thelow frequency side with respect to the center frequency (FC20: 11.86MHz) in the transmission/reception frequency band at −20 dB of theultrasound probe A, and other two intensity peaks located on the highfrequency side with respect to the center frequency (FC20: 11.86 MHz) inthe transmission/reception frequency band at −20 dB of the ultrasoundprobe A.

The pulse duration of the driving waveform F was 194 ns, whichcorresponded to 2.30 periods at the center frequency (FC20: 11.86 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe A.

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform F overlapeach other corresponds to the transmission/reception frequency band at−20 dB of the ultrasound probe A, which was within the range from thelower limit frequency of 3.99 MHz (FL20) to the upper limit frequency of19.72 MHz (FH20). A cover ratio of the ultrasound probe A of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 100%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform F in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe A and the frequency band at −20 dB of thedriving waveform F overlap each other was 0.153 radian. The standarddeviation of the group delays of the driving waveform F in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A and the frequencyband at −20 dB of the driving waveform F overlap each other was 0.0287.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe A obtained asdescribed above and the group delay of the driving waveform F, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform F overlapeach other, was 0.162.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform F.

Comparative Example 4

The above-described ultrasound probe A was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform G illustrated in FIG. 19A. FIG.19B illustrates the frequency power spectrum obtained by the frequencyanalysis of the driving waveform G. FIG. 19C illustrates the group delaycharacteristics of the driving waveform G. In FIG. 19A, the horizontalaxis indicates the time, and the vertical axis indicates the voltage. InFIG. 19B, the horizontal axis indicates the frequency, and the verticalaxis indicates the signal intensity. In FIG. 19C, the horizontal axisindicates the frequency, and the vertical axis indicates the group delayamount.

The driving waveform G had three intensity peaks in thetransmission/reception frequency band (3.99 MHz to 19.72 MHz) at −20 dBof the ultrasound probe A, and two of the intensity peaks located on thelow frequency side with respect to the center frequency (FC20: 11.86MHz) in the transmission/reception frequency band at −20 dB of theultrasound probe A, and remaining one intensity peak located on the highfrequency side with respect to the center frequency (FC20: 11.86 MHz) inthe transmission/reception frequency band at −20 dB of the ultrasoundprobe A.

The pulse duration of the driving waveform G was 225 ns, whichcorresponded to 2.67 periods at the center frequency (FC20: 11.86 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe A.

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform G overlapeach other corresponds to the transmission/reception frequency band at−20 dB of the ultrasound probe A, which was within the range from thelower limit frequency of 3.99 MHz (FL20) to the upper limit frequency of19.72 MHz (FH20). A cover ratio of the ultrasound probe A of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 100%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform G in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe A and the frequency band at −20 dB of thedriving waveform G overlap each other was 0.195 radian. The standarddeviation of the group delays of the driving waveform G in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A and the frequencyband at −20 dB of the driving waveform G overlap each other was 0.0314.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe A obtained asdescribed above and the group delay of the driving waveform G, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform G overlapeach other, was 0.204. FIG. 23 illustrates the totaling result of thegroup delay of the ultrasound probe A and the group delay of the drivingwaveform G.

The second pulse signal was the driving signal of the driving waveformobtained by the inverting the polarity of the driving waveform G.

Comparative Example 5

The above-described ultrasound probe A was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform H illustrated in FIG. 20A. FIG.20B illustrates the frequency power spectrum obtained by the frequencyanalysis of the driving waveform H. FIG. 20C illustrates the group delaycharacteristics of the driving waveform H. In FIG. 20A, the horizontalaxis indicates the time, and the vertical axis indicates the voltage. InFIG. 20B, the horizontal axis indicates the frequency, and the verticalaxis indicates the signal intensity. In FIG. 20C, the horizontal axisindicates the frequency, and the vertical axis indicates the group delayamount.

The driving waveform H had two intensity peaks in thetransmission/reception frequency band (3.99 MHz to 19.72 MHz) at −20 dBof the ultrasound probe A. One intensity peak located on the lowfrequency side, and another intensity peak located on the high frequencyside, with respect to the center frequency (FC20: 11.86 MHz) in thetransmission/reception frequency band at −20 dB of the ultrasound probeA.

The pulse duration of the driving waveform H was 238 ns, whichcorresponded to 2.82 periods at the center frequency (FC20: 11.86 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe A.

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform H overlapeach other was within the range from the lower limit frequency (FL20) of3.99 MHz to the upper limit frequency (FH20) of 16.18 MHz. Concretely,the above upper limit frequency was smaller than the upper limitfrequency of the transmission/reception frequency band at −20 dB of theultrasound probe A, whereas the above lower limit frequency correspondsto the lower limit frequency of the transmission/reception frequencyband at −20 dB of the ultrasound probe A. Thus, this frequency band isnarrower than the transmission frequency band at −20 dB of theultrasound probe A. A cover ratio of the ultrasound probe A of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 77%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform H in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe A and the frequency band at −20 dB of thedriving waveform H overlap each other was 0.172 radian. The standarddeviation of the group delays of the driving waveform H in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A and the frequencyband at −20 dB of the driving waveform H overlap each other was 0.0278.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe A obtained asdescribed above and the group delay of the driving waveform H, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform H overlapeach other, was 0.170.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform H.

Comparative Example 6

The above-described ultrasound probe B was used as the ultrasound probe2.

The first pulse signal output from the transmission section 12 was thedriving signal of the driving waveform H same as that of Comparativeexample 5.

The driving waveform H had two intensity peaks in thetransmission/reception frequency band (3.82 MHz to 19.86 MHz) at −20 dBof the ultrasound probe B. One intensity peak located on the lowfrequency side, and another intensity peak located on the high frequencyside, with respect to the center frequency (FC20: 11.84 MHz) in thetransmission/reception frequency band at −20 dB of the ultrasound probeB.

The pulse duration of the driving waveform H was 238 ns, whichcorresponded to 2.82 periods at the center frequency (FC20: 11.84 MHz)in the transmission/reception frequency band at −20 dB of the ultrasoundprobe B.

The frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeB and the frequency band at −20 dB of the driving waveform H overlapeach other was within the range from the lower limit frequency (FL20) of3.82 MHz to the upper limit frequency (FH20) of 16.18 MHz. Concretely,the above upper limit frequency was smaller than the upper limitfrequency of the transmission/reception frequency band at −20 dB of theultrasound probe B, whereas the above lower limit frequency correspondsto the lower limit frequency of the transmission/reception frequencyband at −20 dB of the ultrasound probe B. Thus, this frequency band isnarrower than the transmission frequency band at −20 dB of theultrasound probe B. A cover ratio of the ultrasound probe B of thisfrequency bandwidth over the transmission/reception frequency bandwidthat −20 dB was 77%.

The difference between the maximum value and the minimum value of thegroup delays of the driving waveform H in the frequency band where thefrequency band included in the transmission/reception frequency band at−20 dB of the ultrasound probe B and the frequency band at −20 dB of thedriving waveform H overlap each other was 0.172 radian. The standarddeviation of the group delays of the driving waveform H in the frequencyband where the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe B and the frequencyband at −20 dB of the driving waveform H overlap each other was 0.0277.

The difference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe B obtained asdescribed above and the group delay of the driving waveform H, in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeB and the frequency band at −20 dB of the driving waveform H overlapeach other, was 0.162.

The second pulse signal was the driving signal of the driving waveformobtained by inverting the polarity of the driving waveform H.

The conditions of the above examples and comparative examples areillustrated in Table 1.

TABLE 1 ULTRASOUND PROBE GROUP DELAY (RADIAN; WITHIN BW20) FL20 FH20FC20 BW20 STANDARD DRIVING WAVEFORM No. [MHz] [MHz] [MHz] [%] DEVIATIONMax − Min No. EXAMPLE 1 A 3.99 19.72 11.86 133 0.0184 0.082 *1 A *2A(APOLARITY INVERSION) EXAMPLE 2 B 3.82 19.86 11.84 135 0.0198 0.082 *1A *2 A(APOLARITY INVERSION) COMPARATIVE C 3.75 20.23 11.99 137 0.02870.154 *1 A EXAMPLE 1 *2 A(APOLARITY INVERSION) COMPARATIVE D 3.96 19.7811.87 133 0.0301 0.200 *1 A EXAMPLE 2 *2 A(APOLARITY INVERSION) EXAMPLE3 A 3.99 19.72 11.88 133 0.0184 0.082 *1 A *2 C EXAMPLE 4 *1 B *2B(APOLARITY INVERSION) EXAMPLE 5 *1 C *2 C(APOLARITY INVERSION) EXAMPLE6 *1 D *2 D(APOLARITY INVERSION) EXAMPLE 7 *1 E *2 E(APOLARITYINVERSION) COMPARATIVE *1 F EXAMPLE 3 *2 F(APOLARITY INVERSION)COMPARATIVE *1 G EXAMPLE 4 *2 G(APOLARITY INVERSION) COMPARATIVE *1 HEXAMPLE 5 *2 H(APOLARITY INVERSION) EXAMPLE 8 B 3.82 19.86 11.84 1350.0198 0.082 *1 B *2 B(APOLARITY INVERSION) EXAMPLE 9 *1 D *2D(APOLARITY INVERSION) COMPARATIVE *1 H EXAMPLE 6 *2 H(APOLARITYINVERSION) DRIVING WAVEFORM GROUP DELAY PROBE + DRIVING WAVEFORM *5(RADIAN; WITHIN BW20) TOTALING OF GROUP DELAYS FL20 FH20 STANDARD(RADIAN: WITHIN BW20) *3 *4 [MHz] [MHz] *6 DEVIATION Max − Min Max − MinEXAMPLE 1 233 2.76 3.99 19.72 100 0.0208 0.0107 0.115 EXAMPLE 2 233 2.763.82 19.86 100 0.0206 0.0107 0.089 COMPARATIVE 233 2.79 3.75 20.23 1000.0206 0.0107 0.152 EXAMPLE 1 COMPARATIVE 233 2.77 3.96 19.78 100 0.02080.0107 0.163 EXAMPLE 2 EXAMPLE 3 233 2.76 3.99 19.72 100 0.0208 0.01070.115 233 2.76 3.99 16.13 77 0.0117 0.079 0.087 EXAMPLE 4 207 2.45 3.9919.72 100 0.0195 0.092 0.120 EXAMPLE 5 233 2.76 3.99 16.13 77 0.01170.079 0.087 EXAMPLE 6 180 2.13 3.99 17.02 83 0.0130 0.065 0.089 EXAMPLE7 180 2.13 3.99 16.88 82 0.0149 0.086 0.127 COMPARATIVE 194 2.30 3.9919.72 100 0.0287 0.153 0.162 EXAMPLE 3 COMPARATIVE 225 2.87 3.99 19.72100 0.0314 0.195 0.204 EXAMPLE 4 COMPARATIVE 238 2.82 3.99 16.18 770.0278 0.172 0.170 EXAMPLE 5 EXAMPLE 8 207 2.45 3.82 19.86 100 0.01940.092 0.134 EXAMPLE 9 180 2.13 3.82 17.02 82 0.0131 0.065 0.076COMPARATIVE 238 2.82 3.82 16.18 77 0.0277 0.172 0.162 EXAMPLE 6 *1:FIRST WAVE TRANSMISSION *2: SECOND WAVE TRANSMISSION *3: PULSE DURATION[nsec] *4 PROBE −20 dB CENTER FREQUENCY CONVERSION WAVENUMBER *5: BANDOF DRIVING WAVEFORM WITHIN PROBE −20 dB BAND *6: COVER RATIO OF DRIVINGWAVEFORM BW20 OVER PROBE −BW20[%]<Evaluation Method>

An SUS wire of 50 μm was embedded in an acoustic equivalent materialpart same as GAMMEX RMI 404GS-LE0.5 at the position of the depth of 15mm. Then the first and second pulse signals of the driving waveforms ofthe conditions illustrated in Table 1 were applied to the same scanningline of the ultrasound probe with a predetermined time interval so thatthe ultrasound probe transmits/receives the first and secondultrasounds, and the reception signals obtained from the received firstand second ultrasounds, respectively, were combined by the pulseinversion method to obtain the ultrasound image according to the TissueHarmonic Imaging (THI). At that time, the transmission focal point was15 mm. Then the wire visualization brightness at the time of imaging wasconverted into a sound intensity (dB) to obtain 20 dB resolution(distance resolution, azimuth resolution). Furthermore, the first andsecond ultrasounds were transmitted/received to the acoustic equivalentmaterial part of GAMMEX RMI 403GS-LE0.5 while the transmission focalpoint was set to 15 mm. The ultrasound images of two consecutive frameswas thus obtained, and a correlation between the ultrasound images oftwo frames was obtained. The depth at the time when the correlation isbelow 0.5 was obtained to be set as a Penetration. Moreover, a carpus,MetacarpoPhalangea (MP) joint flexor tendon, biceps brachii tendon,medial meniscus were visualized under the respective conditions ofExamples 1 to 9 and Comparative examples 1 to 6, and ten personsincluding doctors engaged in orthopedics related business and medicaltechnologists obtain scores according to the following evaluationcriteria, and obtain an average of these values to set the average to avisualization score.

[Evaluation Criteria]

-   10: Visualization degree satisfactory in grasping a condition of    tissue-   8: Visualization degree with no trouble practically in grasping the    condition of tissue-   6: Visualization degree not good but capable of grasping the    condition of tissue-   4: Visualization degree negatively affecting in the grasp of the    condition of tissue-   2: Visualization degree difficult to grasp the condition of tissue

The evaluation result is shown in Table 2.

TABLE 2 EVALUATION RESULT OF IMAGE QUALITY DISTANCE AZIMUTH MP JOINTBICEPS RESOLUTION RESOLUTION PENTRATION FLEXOR BRACHII MEDIAL [μm] [μm][mm] CARPUS TENDON TENDON MENISCUS EXAMPLE 1 190 628 59 9.7 9.8 8.3 8.0EXAMPLE 2 212 640 56 9.4 9.7 8.1 7.8 COMPARATIVE 329 698 49 6.6 7.6 6.85.9 EXAMPLE 1 COMPARATIVE 339 696 50 6.4 7.4 6.4 6.0 EXAMPLE 2 EXAMPLE 3198 630 62 9.6 9.7 8.9 8.6 EXAMPLE 4 222 646 54 9.2 9.6 7.9 7.6 EXAMPLE5 230 660 55 9.0 9.1 7.9 7.6 EXAMPLE 6 220 691 60 8.9 9.6 7.7 8.1EXAMPLE 7 240 689 57 8.6 9.0 7.6 7.9 COMPARATIVE 346 688 52 6.0 5.8 6.66.3 EXAMPLE 3 COMPARATIVE 389 708 49 5.5 6.2 5.6 5.2 EXAMPLE 4COMPARATIVE 341 692 52 5.9 7.0 6.6 6.2 EXAMPLE 5 EXAMPLE 8 244 688 548.4 8.8 7.4 7.6 EXAMPLE 9 222 689 60 8.9 9.6 7.7 8.1 COMPARATIVE 352 67950 6.2 7.3 6.2 6.2 EXAMPLE 6<Evaluation Result>

It was found that from the result in Table 2, Examples 1 to 9 showed thebetter distance resolutions compared with Comparative examples 1 to 6,and the better visualization evaluation compared with comparativeexamples 1 to 6. The specific evaluation result is shown below.

FIG. 25A is a graph illustrating a relationship between the distanceresolution and the difference between the maximum value and the minimumvalue of the totaling values of the group delay of the ultrasound probeand the group delay of the ultrasound probe in the frequency band wherethe frequency band included in the transmission/reception frequency bandat −20 dB of the ultrasound probe and the frequency band at −20 dB ofthe driving waveform overlap each other, obtained from the evaluationresult of Examples 1 to 9 and Comparative examples 1 to 6. According tothis drawing, the resistance resolution was more excellent in the casethat the difference between the maximum value and the minimum value ofthe totaling values of the group delay of the ultrasound probe and thegroup delay of the ultrasound probe was equal to or less than 0.15radian, compared with the case that the difference exceeded 0.15 radian.

FIG. 25B is a graph illustrating a relationship between the total (totalof image quality scores) of visualization evaluation values of thecarpus, MP joint flexor tendon, biceps brachii tendon and medialmeniscus and the difference between the maximum value and the minimumvalue of the totaling results of the group delay of the ultrasound probeand the group delay of the driving waveform in the frequency band wherethe frequency band included in the transmission/reception frequency bandat −20 dB of the ultrasound probe and the frequency band at −20 dB ofthe driving waveform overlap each other, obtained from the evaluationresult of Examples 1 to 9 and Comparative examples 1 to 6. According tothis drawing, the total of the image quality scores in the case that thedifference between the maximum value and the minimum value of thetotaling values of the group delay of the ultrasound probe and the groupdelay of the ultrasound probe was equal to or less than 0.15 radian wasfar higher than that in the case that the difference exceeded 0.15radian.

FIG. 26A is a graph illustrating a relationship between the distanceresolution and the standard deviation of the group delay amounts in thetransmission/reception bandwidth at −20 dB of the ultrasound probe,obtained from the evaluation result of Examples 1 to 2 and Comparativeexamples 1 to 2. According to this drawing, the distance resolution wasmore excellent in the case that the standard deviation of the groupdelay amounts of the ultrasound probe was equal to or less than 0.025,compared with the case that the standard deviation exceeded 0.025.

FIG. 26B is a graph illustrating the relationship between the total ofimage quality scores and the standard deviation of the group delayamounts in the transmission/reception frequency bandwidth at −20 dB ofthe ultrasound probe, obtained from the evaluation result of theExamples 1 to 2 and Comparative examples 1 to 2. According to thisdrawing, the total of the image quality scores in the case that thestandard deviation of the group delays of the ultrasound probe was equalto or less than 0.025 was far higher than that in the case that thestandard deviation exceeded 0.025.

FIG. 27A is a graph illustrating a relationship between the distanceresolution and the difference between the maximum value and the minimumvalue of the group delay amounts in the transmission/reception frequencybandwidth at −20 dB of the ultrasound probe, obtained from theevaluation result of Examples 1 to 2 and Comparative examples 1 to 2.According to this drawing, the distance resolution was more excellent inthe case that the difference between the maximum value and the minimumvalue of the group delay amounts of the ultrasound probe was equal to orless than 0.15 radian, compared with the case that the differenceexceeds 0.15 radian.

FIG. 27B is a graph illustrating a relationship between the total of theimage quality scores and the difference between the maximum value andthe minimum value of the group delay amounts in thetransmission/reception frequency bandwidth at −20 dB of the ultrasoundprobe, obtained from the evaluation result of Examples 1 to 2 andComparative examples 1 to 2. According to this drawing, the total of theimage quality scores in the case that the difference between the maximumvalue and the minimum value of the group delay amounts of the ultrasoundprobe was equal to or less than 0.15 radian was far higher than that inthe case that the difference exceeded 0.15 radian.

FIG. 28A is a graph illustrating a relationship between the distancesolution and the standard deviation of the group delays of the drivingwaveform in the frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band at −20 dB of the driving waveform overlap eachother, obtained from the evaluation result of Examples 1, 3 to 7 andComparative examples 3 to 5. According to this drawing, the distanceresolution was more excellent in the case that the standard deviation ofthe group delays of the driving waveform was equal to or less than0.025, compared with the case that the standard deviation exceeds 0.025.

FIG. 28B is a graph illustrating a relationship between the total of theimage quality scores and the standard deviation of the group delays ofthe driving waveform in the frequency band where the frequency bandincluded in the transmission/reception frequency band at −20 dB of theultrasound probe A and the frequency band at −20 dB of the drivingwaveform overlap each other, obtained from the evaluation result ofExamples 1, 3 to 7 and Comparative examples 3 to 5. According to thisdrawing, the total of the image quality scores in the case that thestandard deviation of the group delays of the driving waveform was equalto or less than 0.025 was far higher than that in the case that thestandard deviation exceeded 0.025.

FIG. 29A is a graph illustrating a relationship between the distanceresolution and the standard deviation of the group delays of the drivingwaveform in the frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeB and the frequency band at −20 dB of the driving waveform overlap eachother, obtained from the evaluation result of Examples 2, 8, 9 andComparative example 6. According to this drawing, the distanceresolution was more excellent in the case that the standard deviation ofthe group delays of the driving waveform was equal to or less than0.025, compared with the case that the standard deviation exceeded0.025.

FIG. 29B is a graph illustrating a relationship between the total of theimage quality scores and the standard deviation of the group delays ofthe driving waveform in the frequency band where the frequency bandincluded in the transmission/reception frequency band at −20 dB of theultrasound probe B and the frequency band at −20 dB of the drivingwaveform overlap with each other, obtained from the evaluation result ofExamples 2, 8, 9 and Comparative example 6. According to this drawing,the total of the image quality scores in the case that the standarddeviation of the group delays of the driving waveform was equal to orless than 0.025 was far higher than that in the case that the standarddeviation exceeded 0.025.

FIG. 30A is a graph illustrating a relationship between the distanceresolution and the difference between the maximum value and the minimumvalue of the group delays of the driving waveform in the frequency bandwhere the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe A and the frequencyband at −20 dB of the driving waveform overlap each other, obtained fromthe evaluation result of Examples 1, 3 to 7 and Comparative examples 3to 5. According to this drawing, the distance resolution was moreexcellent in the case that the difference between the maximum value andthe minimum value of the group delays of the driving waveform was equalto or less than 0.15 radian, compared with the case that the differenceexceeded 0.15 radian.

FIG. 30B is a graph illustrating a relationship between the total of theimage quality scores and the difference between the maximum value andthe minimum value of the group delays of the driving waveform in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeA and the frequency band −20 dB of the driving waveform overlap eachother, obtained from the evaluation result of Examples 1, 3 to 7 andComparative example 3 to 5. According to this drawing, the total of theimage quality scores in the case that the difference between the maximumvalue and the minimum value of the group delays of the driving waveformwas equal to or less than 0.15 radian was far higher than that in thecase that the difference exceeded 0.15 radian.

FIG. 31A is a graph illustrating a relationship between the distancesolution and the difference between the maximum value and the minimumvalue of the group delays of the driving waveform in the frequency bandwhere the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe B and the frequencyband at −20 dB of the driving waveform overlap each other, obtained fromthe evaluation result of Examples 2, 8, 9 and Comparative example 6.According to this drawing, the distance resolution was more excellent inthe case that the difference between the maximum value and the minimumvalue of the group delays of the driving waveform was equal to or lessthan 0.15 radian, compared with the case that the difference exceeded0.15 radian.

FIG. 31B is a graph illustrating a relationship between the total of theimage quality scores and the difference between the maximum value andthe minimum value of the group delays of the driving waveform in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probeB and the frequency band at −20 dB of the driving waveform overlap eachother, obtained from the evaluation result of Examples 2, 8, 9 andComparative example 6. According to this drawing, the total of the imagequality scores in the case that the difference between the maximum valueand the minimum value of the group delays of the driving waveform wasequal to or less than 0.15 radian was far higher than that in the casethat the difference exceeded 0.15 radian.

As described above, according to this embodiments, the ultrasound probe2 is set so that the difference between the maximum value and theminimum value of the group delays obtained from the phase difference foreach frequency between the input pulse signal and the reception signalobtained from the reflected ultrasound of the transmission ultrasoundoutput based on the pulse signal, in the transmission/receptionfrequency band −20 dB of the ultrasound probe 2, becomes equal to orless than 0.15 radian, or so that the standard deviation in thetransmission/reception frequency band at −20 dB of the ultrasound probe2 is equal to or less than 0.025. As a result, unevenness of the groupdelay amounts in the ultrasound probe becomes small in the band in whichthe ultrasounds are transmitted/received, and accordingly cancellationamong the plural kinds of higher harmonic waves is reduced and theultrasound image having the excellent distance resolution can beobtained.

Because the ultrasound probe 2 of this embodiment has −20 dB fractionalbandwidth of 120% or more, further high resolution ultrasound can betransmitted/received.

Moreover, the ultrasound probe 2 of this embodiment outputs thetransmission ultrasound to the test object when receiving the input ofthe pulse signal, and outputs the reception signal when receiving thereflected ultrasound from the test object. The transmission section 12outputs the pulse signal of the predetermined driving waveform so thatthe ultrasound probe 2 creates the transmission ultrasound. Thetransmission section 12 outputs the pulse signal according to which thedifference between the maximum value and the minimum value of the groupdelays obtained from the phase difference for each frequency in thefrequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probe2 and the frequency band at −20 dB of the driving waveform in the pulsesignal overlap each other is equal to or less than 0.15 radian, oraccording to which the standard deviation in the frequency band wherethe frequency band included in the transmission/reception frequency bandat −20 dB of the ultrasound probe and the frequency band at −20 dB ofthe driving signal in the pulse signal overlap each other is equal to orless than 0.025. As a result, unevenness of the group delay amounts inthe driving waveform becomes small in the band where the ultrasounds aretransmitted/received, and accordingly cancellation among the multiplekinds of the higher harmonic waves is reduced and the ultrasound imagehaving the excellent distance resolution can be obtained.

Furthermore, the ultrasound probe 2 of this embodiment outputs thetransmission ultrasound to a test object when receiving the input of thepulse signal, and outputs the reception signal when receiving thereflected ultrasound from the test object. The transmission section 12outputs the pulse signal of the predetermined driving waveform so as tocause the ultrasound probe 2 to generate the transmission ultrasound.The ultrasound probe 2 and the driving waveform of the pulse signaloutput from the transmission section 12 are set so that the differencebetween the maximum value and the minimum value of the totaling valuesof the group delay obtained from the phase difference for each frequencybetween the pulse signal input to the ultrasound probe 2 and thereception signal obtained from the reflected ultrasound of thetransmission ultrasound output based on the pulse signal, and the groupdelay obtained from the phase difference for each frequency of the pulsesignal output by the transmission section 12, in the frequency bandwhere the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe 2 and the frequencyband at −20 dB of the driving signal in the pulse signal becomes equalto or less than 0.015 radian. As a result, unevenness of the group delayamounts in the reception signal becomes small at the time oftransmitting/receiving the ultrasound in the band in which theultrasound is transmitted/received, and accordingly cancellation amongthe multiple kinds of the higher harmonic waves is reduced and theultrasound image having the excellent distance resolution was obtained.

Moreover, the ultrasound probe 2 of this embodiment is set so that thedifference between the maximum value and the minimum value of the groupdelays obtained from the phase difference in each frequency between theinput pulse signal and the reception signal obtained from the reflectedultrasound of the transmission ultrasound output based on the pulsesignal, in the transmission/reception frequency band at −20 dB of theultrasound probe 2, is equal to or less than 0.15 radian, or so that thestandard deviation in the transmission/reception frequency band at −20dB of the ultrasound probe 2 is equal to or less than 0.025. Thetransmission section 12 outputs the pulse signal of the driving waveformaccording to which the difference of the maximum value and the minimumvalue of the group delays obtained from the phase difference in eachfrequency in the frequency band where the frequency band included in thetransmission/reception frequency band at −20 dB of the ultrasound probe2 and the frequency band at −20 dB of the driving waveform in the pulsesignal overlap each other is equal to or less than 0.15 radian, oraccording to which the standard deviation in the frequency band wherethe frequency band included in the transmission/reception frequency bandat −20 dB of the ultrasound probe 2 and the frequency band at −20 dB ofthe driving waveform in the pulse signal overlap each other is equal toor less than 0.025. As a result, unevenness of the group delay amountsin the ultrasound probe and unevenness of the group delay amounts in thedriving waveform become small. Thus, the unevenness of the group delayamounts in the reception signals becomes small. Therefore, designing isfacilitated and the ultrasound image having the excellent distanceresolution can be obtained.

Furthermore, the transmission section 12 of this embodiment outputs thepulse signal of the driving signal in which the frequency bandwidthwhere the frequency band included in the transmission/receptionfrequency band at −20 dB of the ultrasound probe 2 and the frequencyband at −20 dB of the driving waveform in the pulse signal overlap eachother convers 70% or more of the transmission/reception frequencybandwidth at −20 dB of the ultrasound probe 2. As a result, broadbandultrasounds can be transmitted/received.

Moreover, the transmission section 12 of this embodiment outputs thepulse signal whose period is equal to or more than 1.5. As a result, themaximum output voltage at the time of outputting the pulse signal can besuppressed, and the costs can be reduced.

Furthermore, the transmission section 12 of this embodiment outputs thepulse signal of the driving waveform whose pulse duration is equal to ormore than the time corresponding to two periods at the center frequencyof the transmission/reception frequency band at −20 dB of the ultrasoundprobe 2. As a result, the maximum output voltage at the time ofoutputting the pulse signal can be suppressed, and the costs can bereduced.

Moreover, the transmission section 12 of this embodiment outputs thepulse signal by the control signal of five values or less. As a result,the distance resolution can be improved at low costs.

Furthermore, the transmission section 12 of this embodiment outputs thepulse signals of difference driving waveforms to the same scanning linewith a predetermined time interval, for plural times. The imagegenerating section 14 combines the reception signals obtained from thereflected ultrasounds of the transmission ultrasounds generated by thepulse signals of plural times to generate the ultrasound image databased on the combined reception signals. As a result, the broadbandreception of higher harmonic waves can be achieved in the pulseinversion method, and the ultrasound image having further-improveddistance resolution can be obtained at low costs.

Moreover, the transmission section 12 of this embodiment outputs thepulse signals of the driving waveforms having the asymmetricrelationship with each other to the same scanning line with apredetermined time interval for plural times. As a result, thepenetration can be improved while maintaining the resolution withoutproviding a transmission driving device having an advancedpositive/negative driving symmetric property.

Furthermore, the transmission section 12 outputs the pulse signal whichincludes the intensity peaks of the frequency power spectrum on the lowfrequency side and the high frequency side with respect to the centerfrequency of the transmission/reception frequency band at −20 dB of theultrasound probe 2. As a result, broadband wave transmission becomespossible. Thus, not only high-order higher harmonic components but alsodifference tone components can be utilized, and broadband higherharmonic waves can be received. Accordingly, the distance resolution isimproved.

Moreover, the transmission section 12 of this embodiment outputs thepulse signal including two or more of the intensity peaks of thefrequency power spectrum on the high frequency side with respect to thecenter frequency of the transmission/reception frequency band at −20 dBof the ultrasound probe 2. As a result, higher harmonic wave with awider band can be received, and the distance resolution is furtherimproved.

Incidentally, the descriptions of the embodiments of the presentinvention are mere examples of the ultrasound image diagnosis apparatusof the present invention, and the present invention is not limited tothose. The detailed configurations and operations of the respectivefunctional sections constituting the ultrasound image diagnosisapparatus can be arbitrary changed.

The present U.S. patent application claims a priority under the ParisConvention of Japanese patent application No. 2014-082675 filed on Apr.14, 2014, in which all contents of this application are disclosed, andwhich shall be a basis of correction of an incorrect translation.

What is claimed is:
 1. An ultrasound probe comprising: a laminationincluding a backing layer, a piezoelectric layer including oscillators,and an acoustic matching layer; an ultrasound input and output unit tooutput a transmission ultrasound to a test object in response to aninput of a pulse signal; and a signal input and output unit to output areception signal when the ultrasound input and output unit receives areflected ultrasound from the test object, wherein the ultrasound probeis configured so that a difference between a maximum value and a minimumvalue of a group delay in a transmission and reception frequency band at−20 dB of the ultrasonic probe is equal to or less than 0.15 radian, thegroup delay being obtained from a phase difference for each frequencybetween the input pulse signal and the reception signal obtained fromthe reflected ultrasound of the transmission ultrasound output by thepulse signal, or so that a standard deviation of the group delay in thetransmission and reception frequency band at −20 dB of the ultrasonicprobe is equal to or less than 0.025, by at least one of the settingcharacteristics of piezoelectric material applied to the oscillators,setting damping performance and/or acoustic reflection performance ofbacking material composing the backing layer, setting the number ofsheets of the acoustic matching material composing the acoustic matchinglayer, or setting acoustic impedance and thickness of the acousticmatching material.
 2. The ultrasound probe of claim 1, wherein afractional bandwidth at −20 dB is 120% or more.
 3. A method of producingthe ultrasound probe recited in claim 1, including the steps of:laminating a backing layer, a piezoelectric layer, and acoustic matchinglayer, and an acoustic lens, wherein the piezoelectric layer includesoscillators; and adjusting frequency characteristics and group delaycharacteristics of the ultrasound probe by at least one of the settingcharacteristics of piezoelectric material applied to the oscillators,setting damping performance and/or acoustic reflection performance ofbacking material composing the backing layer, setting the number ofsheets of the acoustic matching material composing the acoustic matchinglayer, or setting acoustic impedance and thickness of the acousticmatching material so that at least one of: a difference between amaximum value and a minimum value of a group delay in the transmissionand reception frequency band at −20 dB of the ultrasound probe is equalto or less than 0.15 radian, the group delay being obtained from a phasedifference in each frequency between the input pulse signal and thereception signal obtained from the reflected ultrasound of thetransmission ultrasound output by the pulse signal, or so that astandard deviation of the group delay in the transmission and receptionfrequency band at −20 dB of the ultrasound probe is equal to or lessthan 0.025, or a difference between a maximum value and a minimum valueof a group delay obtained from a phase difference in each frequency inthe frequency band where the transmission and reception frequency bandat −20 dB of the ultrasound probe and the frequency band at −20 dB ofthe driving waveform in a pulse signal overlap each other is equal to orless than 0.15 radian, or a standard deviation of the group delay in thefrequency band where the transmission and reception frequency band at−20 dB of the ultrasound probe and the frequency band at −20 dB of thedriving waveform in the pulse signal overlap each other is equal to orless than 0.025.
 4. The ultrasound probe of claim 1, wherein a frequencybandwidth where the frequency band of the ultrasound probe and afrequency band of the pulse signal overlap each other is at least 70% ofthe transmission and reception frequency bandwidth at −20 dB of theultrasound probe.
 5. An ultrasound image diagnosis apparatus comprising:an ultrasound probe which outputs at least one transmission ultrasoundto a test object in response to an input of at least one pulse signal,and outputs at least one reception signal when at least one reflectedultrasound from the test object is received; and a transmission sectionwhich outputs a pulse signal of a predetermined driving waveform so asto cause the ultrasound probe to generate the transmission ultrasound,wherein the ultrasound probe has a transmission and reception frequencyband at −20 dB and the driving waveform has a frequency band at −20 dB,wherein the transmission section outputs the pulse signal of the drivingwaveform according to which a difference between a maximum value and aminimum value of a group delay obtained from a phase difference in eachfrequency in a frequency band where the transmission and receptionfrequency band at −20 dB of the ultrasound probe and the frequency bandat −20 dB of the driving waveform in the pulse signal overlap each otheris equal to or less than 0.15 radian, or according to which a standarddeviation of the group delay in the frequency band where thetransmission and reception frequency band at −20 dB of the ultrasoundprobe and the frequency band at −20 dB of the driving waveform in thepulse signal overlap each other is equal to or less than 0.025.
 6. Theultrasound image diagnosis apparatus of claim 5, wherein thetransmission section outputs the pulse signal of the driving waveform inwhich the frequency band where the transmission and reception frequencyband at −20 dB of the ultrasound probe and the frequency band at −20 dBof the driving waveform in the pulse signal overlap each other covers70% or more of the transmission and reception frequency bandwidth at −20dB of the ultrasound probe.
 7. The ultrasound image diagnosis apparatusof claim 5, wherein the transmission section outputs the pulse signal ofthe driving waveform whose period is equal to or more than 1.5.
 8. Theultrasound image diagnosis apparatus of claim 5, wherein thetransmission section outputs the pulse signal of the driving waveformwhose pulse duration is equal to or more than a time corresponding totwo periods at a center frequency of the transmission and receptionfrequency band at −20 dB of the ultrasound probe.
 9. The ultrasoundimage diagnosis apparatus of claim 5, wherein the transmission sectionoutputs the pulse signal according to a control signal of five values orless.
 10. The ultrasound image diagnosis apparatus of claim 5, whereinthe transmission section outputs the pulse signals of different drivingwaveforms to a same scanning line with a predetermined time interval forplural times, and wherein the ultrasound image diagnosis furtherincludes an image generating section to combine the reception signalsobtained from the reflected ultrasounds of the transmission ultrasoundsgenerated by the plural pulse signals to generate an ultrasound imagedata based on the combined reception signals.
 11. The ultrasound imagediagnosis apparatus of claim 10, wherein the transmission sectionoutputs the pulse signals whose driving waveforms have an asymmetricrelationship with each other to the same scanning line with thepredetermined time interval for plural times.
 12. The ultrasound imagediagnosis apparatus of claim 5, wherein the transmission section outputsthe pulse signal including intensity peaks of a frequency power spectrumon a low frequency side and on a high frequency side with respect to acenter frequency of the transmission and reception frequency band at −20dB of the ultrasonic probe.
 13. The ultrasound image diagnosis apparatusof claim 12, wherein the transmission section outputs the pulse signalincluding two or more of intensity peaks of a frequency power spectrumon the high frequency side with respect to the center frequency of thetransmission and reception frequency band at −20 dB of the ultrasoundprobe.
 14. The ultrasound image diagnosis apparatus of claim 5, whereina fractional bandwidth at −20 dB of the ultrasound probe is 120% ormore.
 15. An ultrasound image diagnosis apparatus comprising: anultrasound probe which outputs a transmission ultrasound to a testobject in response to an input of a pulse signal, and outputs areception signal when a reflected ultrasound from the test object isreceived, the ultrasound probe comprising a lamination including abacking layer, a piezoelectric layer including oscillators, and anacoustic matching layer; and a transmission section which outputs apulse signal of a predetermined driving waveform so as to cause theultrasound probe to generate the transmission ultrasound, wherein theultrasound probe has a transmission and reception frequency band at −20dB and the driving waveform has a frequency band at −20 dB, wherein theultrasound probe and the driving waveform of the pulse signal outputfrom the transmission section are set so that a difference between amaximum value and a minimum value of a totaling value in a frequencyband where the transmission and reception frequency band at −20 dB ofthe ultrasound probe and the frequency band at −20 dB of the drivingwaveform in the pulse signal overlap each other is equal to or less than0.15 radian, the totaling value being obtained by totalizing a groupdelay obtained from a phase difference in each frequency between thepulse signal input to the ultrasound probe and the reception signalobtained from the reflected ultrasound of the transmission ultrasoundoutput by the pulse signal and a group delay obtained from a phasedifference in each frequency of the pulse signal output by thetransmission section, the ultrasound probe being set by at least one ofthe setting characteristics of piezoelectric material applied to theoscillators, setting damping performance and/or acoustic reflectionperformance of backing material composing the backing layer, setting thenumber of sheets of the acoustic matching material composing theacoustic matching layer, or setting acoustic impedance and thickness ofthe acoustic matching material.
 16. The ultrasound image diagnosisapparatus of claim 15, wherein the ultrasound probe is set so that adifference between a maximum value and a minimum value of a group delayin the transmission and reception frequency band at −20 dB of theultrasound probe is equal to or less than 0.15 radian, the group delaybeing obtained from a phase difference in each frequency between theinput pulse signal and the reception signal obtained from the reflectedultrasound of the transmission ultrasound output by the pulse signal, orso that a standard deviation of the group delay in the transmission andreception frequency band at −20 dB of the ultrasound probe is equal toor less than 0.025, and wherein the transmission section outputs thepulse signal of the driving waveform according to which a differencebetween a maximum value and a minimum value of a group delay obtainedfrom a phase difference in each frequency in the frequency band wherethe transmission and reception frequency band at −20 dB of theultrasound probe and the frequency band at −20 dB of the drivingwaveform in the pulse signal overlap each other is equal to or less than0.15 radian, or a standard deviation of the group delay in the frequencyband where the transmission and reception frequency band at −20 dB ofthe ultrasound probe and the frequency band at −20 dB of the drivingwaveform in the pulse signal overlap each other is equal to or less than0.025.
 17. The ultrasound image diagnosis apparatus of claim 15, whereina frequency bandwidth where the frequency band of the ultrasound probeand the frequency band of the pulse signal overlap each other is atleast 70% of the transmission and reception frequency bandwidth at −20dB of the ultrasound probe.
 18. The ultrasound image diagnosis apparatusof claim 15, wherein a fractional bandwidth at −20 dB of the ultrasoundprobe is 120% or more.